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PHP str_replace function

The PHP function str_replace will replace all occurrences of a given text or texts ($search) in a string ($subject) or array of strings with a string given as a parameter/s ($replace).

Description / Descripción
array|string $search,
array|string $replace,
string|array $subject,
int &$count = null
): string|array
Sintaxis / Sintax
$replaced =str_replace($search, $replace, $subject);
$replaced =str_replace($search, $replace, $subject, $count); 


$search – the value to be searched for within $subject, $search can be an array to perform multiple searches.

$replace – the value by which the value $search will be replaced if found. An array can be used for multiple replacements.

$subject – is the string or array where the values of $search will be searched for and replaced by the values of $replace.

$count – the number of replacements to be made.

Cases that we would have to take into account if any of the parameters is an array

$search(array), $replace(array)

If $search is an array and $replace is also an array, it will use these arrays to replace the values in $subject.

In case that $replace has fewer values than $search, then empty strings “” will be used for the remaining values of $replace.


If $search is an array and $replace is a string, the string will be used for all the values in $search.


If $subject is an array, then the replacements between $search and $replace will be made for each element of $subject, and the returned value is an array with the changes.


Returns a string or an array with specified values replaced.

PHP str_replace examples

In the examples, we will see the most common case where we can use str_replace, and then we will see the cases where the parameters are arrays:

The most commonly used form of str_replace is to change all spaces in " " to "", this is used in the inputs for registration.

$sin_espacios= str_replace(' ', '', $input);

Let’s see what happens when $replace and $search are arrays.

Ejemplo de str_replace con $search y $replace siendo arrays
// ejemplo de str_replace $search(array) y $replace(array)
$mystring ="Aquí me pongo a cantar,
al compás de la vigüela
que el hombre que lo desvela
una pena extraordinaria,
como la ave solitaria
con el cantar se consuela.";

$newstring = str_replace(array("solitaria","pongo"),array("aislada","situo"),$mystring);

Aquí me situo a cantar,
al compás de la vigüela
que el hombre que lo desvela
una pena extraordinaria,
como la ave aislada
con el cantar se consuela.

If all the parameters are arrays, we could have an example like the following:

str_replace con todos los parametros siendo array
$buscar = array("a", "b", "c");
$reemplazar = array("x", "y", "z");
$frase = array("La rapidez del abecedario.", "abc abc abc");

$fraseNueva = str_replace($buscar, $reemplazar, $frase);

    [0] => Lx rxpidez del xyezedxrio.
    [1] => xyz xyz xyz
Note that str_replace can be used in conjunction with PHP’s trim function for form inputs.
Category: en-php
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