strstr

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

strstr — Encuentra la primera aparición de un string

Descripción

strstr(string $haystack, mixed $needle, bool $before_needle = false): string

Devuelve parte del string haystack iniciando desde e incluyendo la primera aparición de needle (aguja) hasta el final del haystack (pajar).

Nota:
Esta función es sensible a mayúsculas. Para búsquedas sin importar las mayúsculas, use stristr().

Nota:
Si solo se quiere saber si un needle determinado aparece en un haystack, se utiliza la función strpos() que es más rápida y requiere menos memoria.

Parámetros

haystack: El string en donde buscar.
needle: Si needle no es una cadena, se convierte a un entero y se aplica como el valor ordinal de un carácter. Este comportamiento está obsoleto a partir de PHP 7.3.0, por lo que su uso está totalmente desaconsejado. Dependiendo del comportamiento previsto, needle deberá ser convertido explícitamente a string, o realizar una llamada explícita a chr().
before_needle: Si se define como true, strstr() devolverá la parte del haystack antes de la primera ocurrencia de needle (excluyendo el needle).

Valores devueltos

Devuelve una parte de un string o false si no se encuentra el needle.

Historial de cambios

Versión	Descripción
5.3.0	Se añadió el parámetro opcional `before_needle`.
4.3.0	strstr() se hizo segura binariamente.

Ejemplos

Ejemplo #1 Ejemplo de strstr()

<?php
$email  = 'name@example.com';
$domain = strstr($email, '@');
echo $domain; // mostrará @example.com

$user = strstr($email, '@', true); // Desde PHP 5.3.0
echo $user; // mostrará name
?>

Ver también

stristr() - strstr insensible a mayúsculas y minúsculas
strrchr() - Encuentra la última aparición de un caracter en un string
strpos() - Encuentra la posición de la primera ocurrencia de un substring en un string
strpbrk() - Buscar una cadena por cualquiera de los elementos de un conjunto de caracteres
preg_match() - Realiza una comparación con una expresión regular

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User Contributed Notes 10 notes

down

laszlo dot heredy at gmail dot com ¶

11 years ago


strstr() is not a way to avoid type-checking with strpos().

If $needle is the last character in $haystack, and testing $needle as a boolean by itself would evaluate to false, then testing strstr() as a boolean will evaluate to false (because, if successful, strstr() returns the first occurrence of $needle along with the rest of $haystack).

<?php
findZero('01234');  // found a zero
findZero('43210');  // did not find a zero
findZero('0');      // did not find a zero
findZero('00');     // found a zero
findZero('000');    // found a zero
findZero('10');     // did not find a zero
findZero('100');    // found a zero

function findZero($numberString) {
    if (strstr($numberString, '0')) {
        echo 'found a zero';
    } else {
        echo 'did not find a zero';
    }
}
?>

Also, strstr() is far more memory-intensive than strpos(), especially with longer strings as your $haystack, so if you are not interested in the substring that strstr() returns, you shouldn't be using it anyway. 

There is no PHP function just to check only _if_ $needle occurs in $haystack; strpos() tells you if it _doesn't_ by returning false, but, if it does occur, it tells you _where_ it occurs as an integer, which is 0 (zero) if $needle is the first part of $haystack, which is why testing if (strpos($needle, $haystack)===false) is the only way to know for sure if $needle is not part of $haystack.

My advice is to start loving type checking immediately, and to familiarize yourself with the return value of the functions you are using.

Cheers.

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xslidian at lidian dot info ¶

11 years ago


For those in need of the last occurrence of a string:

<?php
function strrstr($h, $n, $before = false) {
    $rpos = strrpos($h, $n);
    if($rpos === false) return false;
    if($before == false) return substr($h, $rpos);
    else return substr($h, 0, $rpos);
}
?>

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Gevorg Melkumyan ¶

3 years ago


Don't  confuse this function with strtr ) I lost like 1 hour on that

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gruessle at gmail dot com ¶

13 years ago


Been using this for years:

<?php
/**
*
* @author : Dennis T Kaplan
*
* @version : 1.0
* Date : June 17, 2007
* Function : reverse strstr()
* Purpose : Returns part of haystack string from start to the first occurrence of needle
* $haystack = 'this/that/whatever';
* $result = rstrstr($haystack, '/')
* $result == this
*
* @access public
* @param string $haystack, string $needle
* @return string
**/

function rstrstr($haystack,$needle)
    {
        return substr($haystack, 0,strpos($haystack, $needle));
    }
?>

You could change it to:
rstrstr ( string $haystack , mixed $needle [, int $start] )
<?php

function rstrstr($haystack,$needle, $start=0)
    {
        return substr($haystack, $start,strpos($haystack, $needle));
    }

?>

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w3b_monk3y at yahoo dot com ¶

15 years ago


If you want to emulate strstr's new before_needle parameter pre 5.3 strtok is faster than using strpos to find the needle and cutting with substr. The amount of difference varies with string size but strtok is always faster.

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brett dot jr dot alton at gmail dot com ¶

17 years ago


For the needle_before (first occurance) parameter when using PHP 5.x or less, try:

<?php
$haystack = 'php-homepage-20071125.png';
$needle = '-';
$result = substr($haystack, 0, strpos($haystack, $needle)); // $result = php
?>

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Julian Egelstaff ¶

1 year ago


Lookout for logic inversion in old code!



In PHP 8, if the needle is an empty string, this function will return 0 (not false), implying the first character of the string matches the needle. Before PHP 8, it would return false when the needle is an empty string.



There other string functions that are affected by similar issues in PHP 8: strpos(), strrpos(), stripos(), strripos(), strchr(), strrchr(), stristr(), and this function, strstr()



If you are checking if the return value === false then you will be misled by this new behaviour. You also need to check if the needle was an empty string. Basically, something like this:



<?php

$result = $needle ? strstr($haystack, $needle) : false;

?>

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-2

trent dot renshaw at objectst dot com dot au ¶

9 years ago


> root at mantoru dot de

PHP makes this easy for you. When working with domain portion of email addresses, simply pass the return of strstr() to substr() and start at 1:

substr(strstr($haystack, '@'), 1);

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-20

root at mantoru dot de ¶

17 years ago


Please note that $needle is included in the return string, as shown in the example above. This ist not always desired behavior, _especially_ in the mentioned example. Use this if you want everything AFTER $needle.

<?php
function strstr_after($haystack, $needle, $case_insensitive = false) {
    $strpos = ($case_insensitive) ? 'stripos' : 'strpos';
    $pos = $strpos($haystack, $needle);
    if (is_int($pos)) {
        return substr($haystack, $pos + strlen($needle));
    }
    // Most likely false or null
    return $pos;
}

// Example
$email = 'name@example.com';
$domain = strstr_after($email, '@');
echo $domain; // prints example.com
?>

down

-25

leo dot nard at free dot fr ¶

19 years ago


When encoding ASCII strings to HTML size-limited strings, sometimes some HTML special chars were cut.



For example, when encoding "��" to a string of size 10, you would get: "à&a" => the second character is cut.



This function will remove any unterminated HTML special characters from the string...



<?php

function cut_html($string)

{

    $a=$string;



    while ($a = strstr($a, '&'))

    {

        echo "'".$a."'\n";

        $b=strstr($a, ';'); 

        if (!$b)

        {

            echo "couper...\n";

            $nb=strlen($a);

            return substr($string, 0, strlen($string)-$nb);

        }

        $a=substr($a,1,strlen($a)-1);

    }

    return $string;

}

?>

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