How to remove all uppercase letters from string in php

Two removal methods: 1. Use preg_replace() to execute a regular expression to search for all uppercase letters and replace them with empty characters. The syntax is "preg_replace('/[A-Z]/','', $str)". 2. Use preg_filter() to execute a regular expression to search for all uppercase letters and replace them with empty characters. The syntax is "preg_filter('/[A-Z]/','',$str)".

The operating environment of this tutorial: windows7 system, PHP version 8.1, DELL G3 computer

In php, you can use preg_replace() or preg_filter() works with regular expressions to remove all uppercase letters in a string.

Regular expression used: /[A-Z]/

Function: Search for all uppercase letters

Method 1: Use preg_replace() for regular replacement

preg_replace() function can perform regular expression search and replacement

Just use preg_replace( ) just execute a regular expression to search for all uppercase letters and replace them with null characters.

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);  
function f($str)
{
    $pattern = &#39;/[A-Z]/&#39;;
	$replacement = &#39;&#39;;
    echo preg_replace($pattern, $replacement, $str)."<br>";

}
$str=&#39;Hello World&#39;;
var_dump($str);
f($str);

$str=&#39;abCdEfG&#39;;
var_dump($str);
f($str);

?>

Method 2: Use preg_filter() for regular replacement

preg_filter() and preg_replace( ) function, you can perform regular expression search and replace.

Just perform a regex to search for all uppercase letters and replace them with null characters.

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);  
function f($str)
{
    $pattern = &#39;/[A-Z]/&#39;;
	$replacement = &#39;&#39;;
    echo "处理后：".preg_filter($pattern, $replacement, $str)."<br><br>";

}
$str=&#39;Hello World&#39;;
echo "原字符串：".$str."<br>";
f($str);

$str=&#39;abCdEfG&#39;;
echo "原字符串：".$str."<br>";
f($str);

?>

Explanation: The difference between preg_replace() and preg_filter()

preg_filter() function only returns the result of successful matching. And preg_replace() returns all results, regardless of whether the match is successful.

Recommended learning: "PHP Video Tutorial"

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