preg_grep

(PHP 4, PHP 5, PHP 7, PHP 8)

preg_grep — 返回匹配模式的数组条目

说明

preg_grep(string $pattern, array $array, int $flags = 0): array|false

返回给定数组array中与模式pattern 匹配的元素组成的数组。

参数

pattern: 要搜索的模式，字符串形式。
array: 输入数组。
flags: 如果设置为PREG_GREP_INVERT，这个函数返回输入数组中与给定模式pattern不匹配的元素组成的数组。

返回值

返回使用array中key做索引的数组。或者在失败时返回 false。

范例

示例 #1 preg_grep() 示例


<?php
// 返回所有包含浮点数的元素
$fl_array = preg_grep("/^(\d+)?\.\d+$/", $array);
?>

参见

PCRE 模式
preg_quote() - 转义正则表达式字符
preg_match_all() - 执行一个全局正则表达式匹配
preg_filter() - 执行一个正则表达式搜索和替换
preg_last_error() - 返回最后一个PCRE正则执行产生的错误代码

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User Contributed Notes 4 notes

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Daniel Klein ¶

9 years ago


A shorter way to run a match on the array's keys rather than the values:

<?php
function preg_grep_keys($pattern, $input, $flags = 0) {
    return array_intersect_key($input, array_flip(preg_grep($pattern, array_keys($input), $flags)));
}
?>

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keithbluhm at gmail dot com ¶

12 years ago


Run a match on the array's keys rather than the values:

<?php

function preg_grep_keys( $pattern, $input, $flags = 0 )
{
    $keys = preg_grep( $pattern, array_keys( $input ), $flags );
    $vals = array();
    foreach ( $keys as $key )
    {
        $vals[$key] = $input[$key];
    }
    return $vals;
}

?>

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amolocaleb at gmail dot com ¶

3 years ago


This may be obvious to most experienced developers,but just in case its not,when using preg_grep to check for whitelisted items ,one must be very careful to explicitly define the regex boundaries or it will fail
<?php
$whitelist = ["home","dashboard","profile","group"];
$possibleUserInputs = ["homd","hom","ashboard","settings","group"];
foreach($possibleUserInputs as  $input)
{
     if(preg_grep("/$input/i",$whitelist)
    {
         echo $input." whitelisted";
    }else{
         echo $input." flawed";
    }

}
?>
This results in:

homd flawed
hom whitelisted
ashboard whitelisted
settings flawed
group whitelisted

I think this is because if boundaries are not explicitly defined,preg_grep looks for any instance of  the substring in the whole array and returns true if found.This is not what we want,so boundaries must be defined.

<?php
foreach($possibleUserInputs as  $input)
{
     if(preg_grep("/^$input$/i",$whitelist)
    {
         echo $input." whitelisted";
    }else{
         echo $input." flawed";
    }

}
?>
this results in:
homd flawed
hom flawed
ashboard flawed
settings flawed
group whitelisted
in_array() will also give the latter results but will require few tweaks if say,the search is to be case insensitive,which is always the case 70% of the time

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-31

Timo Klemm ¶

5 years ago


An even shorter way to run a match on the array's keys rather than the values:

<?php
function preg_grep_keys($pattern, $input, $flags = 0) {
    return array_flip( preg_grep($pattern, array_flip($input), $flags ) );
}
?>

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