php javascript表单验证实现方法

更新时间：2016年11月25日 15:10 点击：2038

<!doctype html public "-//w3c//dtd xhtml 1.0 transitional//en" "http://www.w3.org/tr/xhtml1/dtd/xhtml1-transitional.dtd">
<html>
<head>

<title>sample 1</title>

<style>

body { padding: 10px 0px 0px 0px; }

td
{
padding: 2px 5px;
text-align: left;
}

h4 { margin: 0px; }

input.editfield, select.editfield, textarea.editfield { width: 18em; }

</style>

</head>
<body>
<center>

<input type="hidden" name="form_validation_rules" value="
username password year month day details : empty;
username password : len >= 3;
username password : chnum_;
e-mail: email;
membership : select 0;
year : > 1900;
year month day : date;
sex : radio;
details: len <= 20;
categories[] newsletters[] : cnt >= 2;
agree : terms;
" />

<table>

<tr>
<td style="padding-bottom: 10px;" colspan="2"><h4>sample 1</h4></td>
</tr>

<tr>
<td>username:</td>
<td><input class="editfield" type="text" name="username" /></td>
</tr>

<tr>
<td>password:</td>
<td><input class="editfield" type="password" name="password" /></td>
</tr>

<tr>
<td>membership:</td>
<td>
<select class="editfield" name="membership">
    <option value="0"></option>
    <option value="1">silver</option>
    <option value="2">gold</option>
    <option value="3">platinum</option>
</select>
</td>
</tr>

<tr>
<td>sex:</td>
<td>
<input type="radio" name="sex" value="male" /> male
<input type="radio" name="sex" value="female" /> female
</td>
</tr>

<tr>
<td>details:</td>
<td>
<textarea class="editfield" name="details" rows="4"></textarea>
<br />
<small><span id="details_count">0</span> out of 20 characters</small>
</td>
</tr>

<tr>
<td>categories:</td>
<td>
<select class="editfield" name="categories[]" multiple="multiple" size="4">
    <option value="0">cars</option>
    <option value="1">computers</option>
    <option value="2">dogs</option>
    <option value="3">food</option>
</select>
<br />
<small>use ctrl+mouse to select multiple categories</small>
</td>
</tr>

<tr>
<td>newsletters:</td>
<td>
<input type="checkbox" name="newsletters[]" value="0" /> cars <br />
<input type="checkbox" name="newsletters[]" value="1" /> computers <br />
<input type="checkbox" name="newsletters[]" value="2" /> dogs <br />
<input type="checkbox" name="newsletters[]" value="3" /> food
</td>
</tr>

<tr>
<td></td>
<td>
<input type="checkbox" name="agree" />
<small>by checking this box you agree to some terms</small>
</td>
</tr>

</table>

</form>

// ***** data arrays ***********************************************************

// ***** options *****

var form_validation_options =
{
"override_enter" : true,
"override_bksp" : true
};

// ***** messages *****

var form_validation_alerts =
{
    '>'      : "%%name%% should be more than %%num%%!",
    '<'      : "%%name%% should be less than %%num%%!",
    '>='     : "%%name%% should be more or equal to %%num%%!",
    '<='     : "%%name%% should be less or equal to %%num%%!",
    'ch'     : "%%name%% contains invalid characters!",
    'chnum_' : "%%name%% contains invalid characters!",
    'cnt >' : "you should select more than %%num%% %%name%%!",
    'cnt <' : "you should select less than %%num%% %%name%%!",
    'cnt >=' : "you should select at least %%num%% %%name%%!",
    'cnt <=' : "you should select at most %%num%% %%name%%!",
    'cnt ==' : "you should select %%num%% %%name%%!",
    'date'   : "please, enter a valid %%name%%!",
    'email' : "please, enter a valid e-mail address!",
    'empty' : "please, enter %%name%%!",
    'len >' : "%%name%% should contain more than %%num%% characters!",
    'len <' : "%%name%% should contain less than %%num%% characters!",
    'len >=' : "%%name%% should contain at least %%num%% characters!",
    'len <=' : "%%name%% should contain at most %%num%% characters!",
    'len ==' : "%%name%% should contain %%num%% characters!",
    'num'    : "%%name%% is not a valid number!",
    'radio' : "please, select %%name%%!",
    'select' : "please, select %%name%%!",
    'terms' : "you must agree to the terms first!"
};

// ***** form field types *****

var form_validation_nonedit = ' button hidden reset submit ';
var form_validation_edit    = ' checkbox file password radio select-multiple select-one text textarea ';
var form_validation_type    = ' file password text textarea ';
var form_validation_check   = ' checkbox radiox select-multiple select-one ';

// ***** alert *****************************************************************

function form_validation_alert(type, name, num)
{
name = name.replace(/^w*(w*)w*$/, "$1");

msg = form_validation_alerts[type];
msg = msg.replace('%%name%%', name.substr(0, 1).touppercase()+name.substr(1, name.length-1).tolowercase());
msg = msg.replace('%%name%%', name.tolowercase());
msg = msg.replace('%%num%%', num);

alert(msg);

return false;
}

// ***** behave ****************************************************************

function form_validation_behave(control, key, rules)
{
rules = form_validation_rules2array(rules);

for (var i = 0; i < rules.length; i++)
{
var rule = rules[i].split(/s*:s*/);

if (rule.length < 2) continue;
if (!form_validation_instring(' '+rule[0]+' ', control.name)) continue;

rule[1] = rule[1].split(/s+/);

    switch (rule[1][0])
    {
      // ***** count *****

      case 'count':
        document.getelementbyid(rule[1][1]).innerhtml = control.value.length;
        if (rule[1].length >= 5)
          if (control.value.length < rule[1][2])
               document.getelementbyid(rule[1][1]).style.color = rule[1][3];
          else document.getelementbyid(rule[1][1]).style.color = rule[1][4];
        break;

// ***** next *****

      case 'next':
        if (control.value.length == rule[1][1]) form_validation_focusnext(control);
        break;

// ***** prev *****

      case 'prev':
        if (control.value.length == 0 && key == 8) form_validation_focusprev(control);
        break;
    }
}

return true;
}

// ***** getelement ************************************************************

function form_validation_getelement(tag, name)
{
for (var i = 0; i < tag.elements.length; i++)
if (tag.elements[i].name == name) return tag.elements[i];
return undefined;
}

// ***** instring **************************************************************

function form_validation_instring(str, val)
{
return str.indexof(' '+val+' ') >= 0;
}

// ***** focusnext *************************************************************

function form_validation_focusnext(tag)
{
for (var i = 0; i < tag.form.elements.length; i++)
    if (tag.form.elements[i] == tag)
      for (var j = i+1; j < tag.form.elements.length; j++)
        if (form_validation_instring(form_validation_edit, tag.form.elements[j].type))
        {
          if (form_validation_instring(form_validation_type, tag.form.elements[j].type))
               form_validation_setselection(tag.form.elements[j], 0, 0, 'frend');
          else tag.form.elements[j].focus();
          return false;
        }

return true;
}

// ***** focusprev *************************************************************

function form_validation_focusprev(tag)
{
for (var i = 0; i < tag.form.elements.length; i++)
    if (tag.form.elements[i] == tag)
      for (var j = i-1; j >= 0; j--)
        if (form_validation_instring(form_validation_edit, tag.form.elements[j].type))
        {
          if (form_validation_instring(form_validation_type, tag.form.elements[j].type))
               form_validation_setselection(tag.form.elements[j], 0, 0, 'frend');
          else tag.form.elements[j].focus();
          return false;
        }

return true;
}

// ***** initialize ************************************************************

function form_validation_initialize(control, rules)
{
rules = form_validation_rules2array(rules);

for (var i = 0; i < rules.length; i++)
{
var rule = rules[i].split(/s*:s*/);

if (rule.length < 2) continue;
if (!form_validation_instring(' '+rule[0]+' ', control.name)) continue;

rule[1] = rule[1].split(/s+/);

    switch (rule[1][0])
    {
      // ***** count *****

return true;
}

// ***** onchange **************************************************************

function form_validation_onchange(e)
{
var ie = navigator.appname == "microsoft internet explorer";
var tag = ie ? window.event.srcelement : e.target;

return true;
}

// ***** onkeypress ************************************************************

function form_validation_onkeypress(e)
{
var ie = navigator.appname == "microsoft internet explorer";
var tag = ie ? window.event.srcelement : e.target;
var key = ie ? window.event.keycode : e.which;

if (form_validation_options['override_backspace'])
if (key == 8)
return form_validation_instring(form_validation_type, tag.type);

if (form_validation_options['override_enter'])
if (key == 13 && tag.type != 'textarea')
return form_validation_focusnext(tag);

return true;
}

// ***** onkeyup ***************************************************************

function form_validation_onkeyup(e)
{
var ie = navigator.appname == "microsoft internet explorer";
var tag = ie ? window.event.srcelement : e.target;
var key = ie ? window.event.keycode : e.which;

var behaviours = form_validation_getelement(tag.form, 'form_validation_behaviours');

if (behaviours !== undefined) form_validation_behave(tag, key, behaviours.value);
}

// ***** onsubmit **************************************************************

function form_validation_onsubmit(e)
{
var ie = navigator.appname == "microsoft internet explorer";
var tag = ie ? window.event.srcelement : e.target;
if (tag.tagname != 'form') tag = tag.form;

// ***** validate fields *****

var rules = form_validation_getelement(tag, 'form_validation_rules');

if (rules !== undefined)
    for (var i = 0; i < tag.elements.length; i++)
      if (!form_validation_validate(tag.elements[i], rules.value))
      {
        tag.elements[i].focus();
        if (tag.elements[i].select !== undefined) tag.elements[i].select();
        return false;
      }

// ***** unset fields *****

for (var i = 0; i < tag.elements.length; i++)
{
if (tag.elements[i].name == 'form_validation_rules') tag.elements[i].value = '';
if (tag.elements[i].name == 'form_validation_behaviours') tag.elements[i].value = '';
}

return true;
}

// ***** register **************************************************************

function form_validation_register()
{
for (var i = 0; i < document.forms.length; i++)
    with (document.forms[i])
    {
      var rules      = form_validation_getelement(document.forms[i], 'form_validation_rules');
      var behaviours = form_validation_getelement(document.forms[i], 'form_validation_behaviours');

if (rules === undefined && behaviours === undefined) continue;

onsubmit = form_validation_onsubmit;

      for (var j = 0; j < elements.length; j++)
      {
        if (behaviours !== undefined) form_validation_initialize(elements[j], behaviours.value);

        elements[j].onchange   = form_validation_onchange;
        elements[j].onkeypress = form_validation_onkeypress;
        elements[j].onkeyup    = form_validation_onkeyup;
      }
    }
}

// ***** rules2array ***********************************************************

function form_validation_rules2array(rules)
{
rules = rules.replace(/^(s*)(s.*)/, "$2");
rules = rules.replace(/(.*s)(s*)$/, "$1");
return rules.split(/s*;s*/);
}

// ***** setselection **********************************************************

function form_validation_setselection(control, start, end, mode)
{
if (control.focus) control.focus();

// ***** netscape *****

if (control.selectionstart !== undefined &&
      control.selectionend   !== undefined)
{
    offset = control.selectionstart;
    if (mode == 'frstart') offset = 0;
    if (mode ==   'frend') offset = control.textlength;

control.selectionstart = offset+start;
control.selectionend = offset+end;

return true;
}

// ***** ie *****

if (control.select                 !== undefined &&
      document.selection             !== undefined &&
      document.selection.createrange !== undefined)
{
    if (mode == 'frstart' || mode == 'frend') control.select();

range = document.selection.createrange();

if (mode == 'frstart') range.moveend ("character", -range.text.length);
if (mode == 'frend') range.movestart("character", range.text.length);

    range.movestart("character", start);
    range.moveend ("character", end);
    range.select();

return true;
}

return false;
}

// ***** validate **************************************************************

function form_validation_validate(control, rules)
{
rules = form_validation_rules2array(rules);

for (var i = 0; i < rules.length; i++)
{
var rule = rules[i].split(/s*:s*/);

if (rule.length < 2) continue;
if (!form_validation_instring(' '+rule[0]+' ', control.name)) continue;

rule[1] = rule[1].split(/s+/);

    switch (rule[1][0])
    {
      // ***** comparison *****

      case '>':
        if (control.value == '' || isnan(control.value))
          return form_validation_alert('num', control.name, 0);
        if (control.value <= rule[1][1])
          return form_validation_alert('>', control.name, rule[1][1]);
        break;

      case '<':
        if (control.value == '' || isnan(control.value))
          return form_validation_alert('num', control.name, 0);
        if (control.value >= rule[1][1])
          return form_validation_alert('<', control.name, rule[1][1]);
        break;

      case '>=':
        if (control.value == '' || isnan(control.value))
          return form_validation_alert('num', control.name, 0);
        if (control.value < rule[1][1])
          return form_validation_alert('>=', control.name, rule[1][1]);
        break;

      case '<=':
        if (control.value == '' || isnan(control.value))
          return form_validation_alert('num', control.name, 0);
        if (control.value > rule[1][1])
          return form_validation_alert('<=', control.name, rule[1][1]);
        break;

// ***** ch *****

      case 'ch':
        if (!/^([a-za-z]+)$/.test(control.value))
          return form_validation_alert('ch', control.name, 0);
        break;

// ***** chnum_ *****

      case 'chnum_':
        if (!/^(w+)$/.test(control.value))
          return form_validation_alert('chnum_', control.name, 0);
        break;

// ***** cnt *****

case 'cnt':
var cnt = 0;

        if (control.type == 'select-multiple')
          for (var k = 0; k < control.options.length; k++)
            if (control.options[k].selected) cnt++;

        if (control.type == 'checkbox')
          with (control.form)
            for (var k = 0; k < elements.length; k++)
              if (elements[k].name == control.name && elements[k].checked) cnt++;

        if (rule[1][1] == '>' && cnt <= rule[1][2])
          return form_validation_alert('cnt >', control.name, rule[1][2]);
        if (rule[1][1] == '<' && cnt >= rule[1][2])
          return form_validation_alert('cnt <', control.name, rule[1][2]);
        if (rule[1][1] == '>=' && cnt < rule[1][2])
          return form_validation_alert('cnt >=', control.name, rule[1][2]);
        if (rule[1][1] == '<=' && cnt > rule[1][2])
          return form_validation_alert('cnt >=', control.name, rule[1][2]);
        if (rule[1][1] == '==' && cnt != rule[1][2])
          return form_validation_alert('cnt ==', control.name, rule[1][2]);

break;

// ***** date *****

case 'date':
rule[0] = rule[0].split(/s+/);

        if (rule[0].length == 3)
        {
          var year;
          var month;
          var day;

          with (control.form)
            for (var k = 0; k < elements.length; k++)
            {
              if (elements[k].name == rule[0][0]) year = elements[k];
              if (elements[k].name == rule[0][1]) month = elements[k];
              if (elements[k].name == rule[0][2]) day   = elements[k];
            }

          if (year !== undefined && month !== undefined && day !== undefined)
          {
            if (control == year)
              if (year.value == '' || isnan(year.value))
                return form_validation_alert('date', year.name, 0);
            if (control == month)
              if (month.value == '' || isnan(month.value) || month.value < 0 || month.value > 12)
                return form_validation_alert('date', month.name, 0);
            if (control == day)
            {
              if (day.value   == '' || isnan(day.value)   || day.value   < 0 || day.value   > 31)
                return form_validation_alert('date', day.name, 0);
              date = new date(year.value, month.value, day.value);
              if (date.getdate() != day.value)
                return form_validation_alert('date', day.name, 0);
            }
          }
        }

break;

// ***** email *****

      case 'email':
        if (!/^(w+.)*(w+)@(w+.)+(w+)$/.test(control.value))
          return form_validation_alert('email', control.name, 0);
        break;

// ***** empty *****

      case 'empty':
        if (form_validation_instring(form_validation_type, control.type) && control.value == '')
          return form_validation_alert('empty', control.name, 0);
        break;

// ***** len *****

      case 'len':
        if (rule[1][1] == '>' && control.value.length <= rule[1][2])
          return form_validation_alert('len >', control.name, rule[1][2]);
        if (rule[1][1] == '<' && control.value.length >= rule[1][2])
          return form_validation_alert('len <', control.name, rule[1][2]);
        if (rule[1][1] == '>=' && control.value.length < rule[1][2])
          return form_validation_alert('len >=', control.name, rule[1][2]);
        if (rule[1][1] == '<=' && control.value.length > rule[1][2])
          return form_validation_alert('len <=', control.name, rule[1][2]);
        if (rule[1][1] == '==' && control.value.length != rule[1][2])
          return form_validation_alert('len ==', control.name, rule[1][2]);
        break;

// ***** num *****

      case 'num':
        if (control.value == '' || isnan(control.value))
          return form_validation_alert('num', control.name, 0);
        break;

// ***** radio *****

      case 'radio':
        var checked = false;
        with (control.form)
          for (var k = 0; k < elements.length; k++)
            if (elements[k].name == control.name && elements[k].checked)
              checked = true;
        if (!checked) return form_validation_alert('radio', control.name, 0);

// ***** select *****

      case 'select':
        if (control.value == rule[1][1])
          return form_validation_alert('select', control.name, 0);
        break;

// ***** terms *****

      case 'terms':
        if (!control.checked)
          return form_validation_alert('terms', control.name, 0);
        break;
    }
}

return true;
}

// ***** initialize forms ******************************************************

form_validation_register();
</script>

</center>
</body>
</html>

把下面代码保存成php文件
$form_validation_alerts = array(
    '>'      => "%%name%% should be more than %%num%%!",
    '<'      => "%%name%% should be less than %%num%%!",
    '>='     => "%%name%% should be more or equal to %%num%%!",
    '<='     => "%%name%% should be less or equal to %%num%%!",
    'ch'     => "%%name%% contains invalid characters!",
    'chnum_' => "%%name%% contains invalid characters!",
    'cnt >' => "you should select more than %%num%% %%name%%!",
    'cnt <' => "you should select less than %%num%% %%name%%!",
    'cnt >=' => "you should select at least %%num%% %%name%%!",
    'cnt <=' => "you should select at most %%num%% %%name%%!",
    'cnt ==' => "you should select %%num%% %%name%%!",
    'date'   => "please, enter a valid %%name%%!",
    'email' => "please, enter a valid e-mail address!",
    'empty' => "please, enter %%name%%!",
    'len >' => "%%name%% should contain more than %%num%% characters!",
    'len <' => "%%name%% should contain less than %%num%% characters!",
    'len >=' => "%%name%% should contain at least %%num%% characters!",
    'len <=' => "%%name%% should contain at most %%num%% characters!",
    'len ==' => "%%name%% should contain %%num%% characters!",
    'num'    => "%%name%% is not a valid number!",
    'radio' => "please, select %%name%%!",
    'select' => "please, select %%name%%!",
    'terms' => "you must agree to the terms first!");

function form_validation_alert($type, $name, $num)
{
$name = preg_replace('/^w*(w*)w*$/', "$1", $name);

$msg = $globals['form_validation_alerts'][$type];
$msg = str_replace('%%name%%', strtoupper(substr($name, 0, 1)) . strtolower(substr($name, 1, strlen($name)-1)), $msg);
$msg = str_replace('%%name%%', strtolower($name), $msg);
$msg = str_replace('%%num%%', $num, $msg);

return $msg;
}

// ***** isnan *****************************************************************

function form_validation_isnan($value)
{
return (string)(integer)$value !== (string)$value;
}

// ***** validate **************************************************************

function form_validation_validate($data, $rules)
{
$rules = preg_replace('/^(s*)(s.*)/', "$2", $rules);
$rules = preg_split('/s*;s*/', $rules);

foreach ($rules as $i => $rule)
{
$rule = preg_split('/s*:s*/', $rule);

if (count($rule) < 2) continue;

$rule[0] = preg_split('/s+/', $rule[0]);
$rule[1] = preg_split('/s+/', $rule[1]);

    foreach ($rule[0] as $j => $name)
    {
      $name = str_replace("[]", "", $name);

if (!in_array($rule[1][0], array('cnt', 'radio', 'terms')))
if (!isset($data[$name])) return 'invalid form!';

if (!in_array($rule[1][0], array('cnt')))
if ( isset($data[$name]) && is_array($data[$name])) return 'invalid form!';

      switch ($rule[1][0])
      {
        // ***** comparison *****

        case '>':
          if (form_validation_isnan($data[$name]))
            return form_validation_alert('num', $name, 0);
          if ($data[$name] <= $rule[1][1])
            return form_validation_alert('>', $name, $rule[1][1]);
          break;

        case '<':
          if (form_validation_isnan($data[$name]))
            return form_validation_alert('num', $name, 0);
          if ($data[$name] >= $rule[1][1])
            return form_validation_alert('<', $name, $rule[1][1]);
          break;

        case '>=':
          if (form_validation_isnan($data[$name]))
            return form_validation_alert('num', $name, 0);
          if ($data[$name] < $rule[1][1])
            return form_validation_alert('>=', $name, $rule[1][1]);
          break;

        case '<=':
          if (form_validation_isnan($data[$name]))
            return form_validation_alert('num', $name, 0);
          if ($data[$name] > $rule[1][1])
            return form_validation_alert('<=', $name, $rule[1][1]);
          break;

// ***** ch *****

        case 'ch':
          if (!preg_match('/^([a-za-z]+)$/', $data[$name]))
            return form_validation_alert('ch', $name, 0);
          break;

// ***** chnum_ *****

        case 'chnum_':
          if (!preg_match('/^(w+)$/', $data[$name]))
            return form_validation_alert('chnum_', $name, 0);
          break;

// ***** cnt *****

        case 'cnt':
          $cnt = isset($data[$name]) ? (is_array($data[$name]) ? count($data[$name]) : 1) : 0;
          if ($rule[1][1] == '>' && $cnt <= $rule[1][2])
            return form_validation_alert('cnt >', $name, $rule[1][2]);
          if ($rule[1][1] == '<' && $cnt >= $rule[1][2])
            return form_validation_alert('cnt <', $name, $rule[1][2]);
          if ($rule[1][1] == '>=' && $cnt < $rule[1][2])
            return form_validation_alert('cnt >=', $name, $rule[1][2]);
          if ($rule[1][1] == '<=' && $cnt > $rule[1][2])
            return form_validation_alert('cnt <=', $name, $rule[1][2]);
          break;

// ***** email *****

        case 'email':
          if (!preg_match('/^(w+.)*(w+)@(w+.)+(w+)$/', $data[$name]))
            return form_validation_alert('email', $name, 0);
          break;

// ***** empty *****

        case 'empty':
          if ($data[$name] == '')
            return form_validation_alert('empty', $name, 0);
          break;

// ***** len *****

        case 'len':
          if ($rule[1][1] == '>' && strlen($data[$name]) <= $rule[1][2])
            return form_validation_alert('len >', $name, $rule[1][2]);
          if ($rule[1][1] == '<' && strlen($data[$name]) >= $rule[1][2])
            return form_validation_alert('len <', $name, $rule[1][2]);
          if ($rule[1][1] == '>=' && strlen($data[$name]) < $rule[1][2])
            return form_validation_alert('len >=', $name, $rule[1][2]);
          if ($rule[1][1] == '<=' && strlen($data[$name]) > $rule[1][2])
            return form_validation_alert('len <=', $name, $rule[1][2]);
          break;

// ***** num *****

        case 'num':
          if (form_validation_isnan($data[$name]))
            return form_validation_alert('num', $name, 0);
          break;

// ***** radio *****

        case 'radio':
          if (!isset($data[$name]))
            return form_validation_alert('radio', $name, 0);
          break;

// ***** select *****

        case 'select':
          if (!isset($data[$name]))
            return form_validation_alert('select', $name, 0);
          break;

// ***** terms *****

        case 'terms':
          if (!isset($data[$name]))
            return form_validation_alert('terms', $name, 0);
          break;
      }
    }

// ***** date *****

    if ($rule[1][0] == 'date')
    {
      $year = $rule[0][0];
      $month = $rule[0][1];
      $day   = $rule[0][2];

      if (form_validation_isnan($data[$year ]))
        return form_validation_alert('date', $year, 0);
      if (form_validation_isnan($data[$month]) || $data[$month] < 0 || $data[$month] > 12)
        return form_validation_alert('date', $month, 0);
      if (form_validation_isnan($data[$day ]) || $data[$day ] < 0 || $data[$day ] > 31 || !checkdate($data[$month], $data[$day], $data[$year]))
        return form_validation_alert('date', $day,   0);
    }
}

return true;
}

可变变量名指的是使用一个变量的值作为这个变量的名称。在上面的例子中，通过使用两个$符号，你可以把hello设置成一个变量的名称

例

<?php $a = 'hello'; ?>

，就像下面那样。

<?php $$a = 'world'; ?>

通过上面的两个语句，有两个变量被定义：变量$a，装的内容是”hello” 以及变量$hello，装的内容是 “world”。于是，下面的语言：

<?php echo "$a ${$a}"; ?>

跟下面的语句的输出完全一致：

<?php echo "$a $hello"; ?>

它们都输出：hello world。

*/
$array = explode(',','1101,1102,1103,418,617,712,713,312,313,104,105,106,107,108');
if( in_array('8',$array) )
{
echo 'a';
}
else
{
echo 'b';
}

/*
定义和用法
in_array() 函数在数组中搜索给定的值。

语法
in_array(value,array,type)参数描述
value 必需。规定要在数组搜索的值。
array 必需。规定要搜索的数组。
type 可选。如果设置该参数为 true，则检查搜索的数据与数组的值的类型是否相同。

说明
如果给定的值 value 存在于数组 array 中则返回 true。如果第三个参数设置为 true，函数只有在元素存在于数组中且数据类型与给定值相同时才返回 true。

如果没有在数组中找到参数，函数返回 false。

注释：如果 value 参数是字符串，且 type 参数设置为 true，则搜索区分大小写

这三种方法都是从网上找到了，第一种测试可以，后面二种也可以，不过第一次在不同浏览器可能不兼容。
*/
//方法一
echo "document.write('<script language="javascript" src="/ads/js/$js"></script>');";
//方法二
echo "var s=document.createelement('script');";
echo "s.src='/ads/js/$js'; ";
echo "document.getelementsbytagname('head')[0].appendchild(s);";
//方法三
echo "document.write("<scri'+'pt type='text/javascript' src='/ads/js/$js'></scr'+'ipt>");";

*/
@header("http/1.1 404 not found");
@header("status: 404 not found");
echo 'echo 404';
exit();

/*
查看404是否设置成功可以利用firefox 的firebug插件来查看

查看方法

在已经安装firebug的情况下，用firefox浏览器打开要检查404状态码的页面，点击右下角小虫的图标，启动"网络"标签，依次打开"网络–所有/html–headers"；如果一切正常，你就可以看到包括headers、响应在内的各项页面参数了。

404页面对网站影响

对seo教程的影响并不大。但是有，总比没有好。如果你拥有这个权限，你最好还是设置一下404页面。这个东西跟网站地图一样，不是所有的网站都得设置，但是有时候有设置的必要。

再考虑是不是要设置404页面时，应该多考虑用户体验，而不是seo。

看一下apache 404定义吧

apache里设置404错误页面为apache server设置 404错误页面的方法很简单，只需在.htaccess 文件中加入如下内容即可：errordocument 404 /notfound.php

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