Understanding PHP str_replace(): Syntax, Parameters, and Practical Examples
This article explains the PHP str_replace() function, detailing its syntax, the roles of search, replace, and subject parameters, and demonstrates four common usage patterns—including string-to-string, array-to-string, array-to-array replacements, and counting replacements—while highlighting replacement order effects.
The str_replace() function in PHP replaces occurrences of a search string with a replacement string within a given subject.
Syntax:
str_replace(mixed $search, mixed $replace, mixed $subject [, int &$count]) : mixed1. Both $search and $replace are strings:
<?php
$bodytag = str_replace("%body%", "black", "<body text='%body%'>");
echo $bodytag; // outputs: <body text='black'>
?>2. $search is an array, $replace is a string:
<?php
$vowels = array("a","e","i","o","u","A","E","I","O","U");
$onlyconsonants = str_replace($vowels, "", "Hello World of PHP");
echo $onlyconsonants; // outputs: Hll Wrld f PHP
?>3. Both $search and $replace are arrays:
<?php
$phrase = "You should eat fruits, vegetables, and fiber every day.";
$healthy = array("fruits","vegetables","fiber");
$yummy = array("pizza","beer","ice cream");
$newphrase = str_replace($healthy, $yummy, $phrase);
// outputs: You should eat pizza, beer, and ice cream every day
?>4. Using the optional $count parameter to get the number of replacements:
<?php
$str = str_replace("ll", "", "good golly miss molly!", $count);
echo $count; // 2
?>Note on replacement order: When both $search and $replace are arrays, replacements are performed sequentially from left to right, so earlier replacements can affect later ones. For example:
$search = array('A','B','C','D','E');
$replace = array('B','C','D','E','F');
$subject = 'A';
echo str_replace($search, $replace, $subject); // outputs: FSigned-in readers can open the original source through BestHub's protected redirect.
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