PHPのお勉強！

PHP TOP
PHP 8.4.2 Released!

    preg_grep

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

    preg_grep — パターンにマッチする配列の要素を返す

    説明

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

    array 配列の要素のうち、 指定した pattern にマッチするものを要素とする配列を返します。

    パラメータ

    pattern

    検索するパターンを表す文字列。

    array

    入力の配列。

    flags

    PREG_GREP_INVERT を設定すると、この関数は 与えた pattern にマッチ しない 要素を返します。

    戻り値

    array 配列のキーを使用した配列を返します。 失敗した場合に false を返します

    エラー / 例外

    渡された正規表現のパターンがコンパイルできない場合、E_WARNING が発生します。

    例

    例1 preg_grep() の例

    <?php
    // すべての浮動小数点数を含む配列要素を返す
    $fl_array = preg_grep("/^(\d+)?\.\d+$/", $array);
    ?>

    参考

    Found A Problem?

    Learn How To Improve This Page • Submit a Pull Request • Report a Bug
    ＋add a note

    User Contributed Notes 3 notes

    up
    76
    Daniel Klein
    11 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)));
    }
    ?>
    up
    26
    keithbluhm at gmail dot com
    14 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;
    }

    ?>
    up
    14
    amolocaleb at gmail dot com
    6 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
    ＋add a note
    To Top