strstr

(PHP 4, PHP 5)

strstr — 查找字符串的首次出现

说明

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

返回 haystack 字符串从 needle 第一次出现的位置开始到 haystack 结尾的字符串。

Note:

该函数区分大小写。如果想要不区分大小写，请使用 stristr() 。

Note:

如果你仅仅想确定 needle 是否存在于 haystack 中，请使用速度更快、耗费内存更少的 strpos() 函数。

参数

haystack: 输入字符串。
needle: 如果 needle 不是一个字符串，那么它将被转化为整型并且作为字符的序号来使用。
before_needle: 若为 TRUE ， strstr() 将返回 needle 在 haystack 中的位置之前的部分。

返回值

返回字符串的一部分或者 FALSE （如果未发现 needle）。

更新日志

版本	说明
5.3.0	新增可选的 `before_needle` 参数。
4.3.0	strstr() 成为二进制安全的。

范例

Example #1 strstr() 范例

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

 $user  =  strstr ( $email ,  '@' ,  true );  // 从 PHP 5.3.0 起
 echo  $user ;  // 打印 name
 ?>

参见

preg_match() - 执行一个正则表达式匹配
stristr() - strstr 函数的忽略大小写版本
strpos() - 查找字符串首次出现的位置
strrchr() - 查找指定字符在字符串中的最后一次出现
substr() - 返回字符串的子串

用户评论:

[#1] trent dot renshaw at objectst dot com dot au [2015-06-25 02:08:14]

> 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);

[#2] laszlo dot heredy at gmail dot com [2013-11-07 21:39:20]

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.

[#3] xslidian at lidian dot info [2013-02-21 07:37:48]

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); } ?>

[#4] peter at olds dot co [2012-02-20 10:16:48]

I was in need of getting the first and last part of a string pre 5.3 so I wrote this:

<?php $fir = $first = explode( " ", $cmd[1] ); unset( $fir[0] ); $end = ltrim( implode( " ", $fir ) ); ?>

I needed it split with a " " but can obviously change for your needs. But with this format your output for the string:

"PHP is the best programming language out there"

Will give you the following results:

<?php $first[0] // PHP $end // is the best programming language out there ?>

Works really well :)

[#5] gruessle at gmail dot com [2011-04-20 13:39:51]

Been using this for years:

<?php 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)); } ?>

[#6] w3b_monk3y at yahoo dot com [2009-01-20 00:28:04]

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.

[#7] brett dot jr dot alton at gmail dot com [2007-11-25 08:02:35]

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 ?>

[#8] prafe at prafesplace dot com [2007-11-21 21:14:39]

If you want to use the $before_needle parameter that's only in PHP 5.3.0, I found a way to use it in lower versions.

The code is a bit hefty, but it works. It also has added $include_needle and $case_sensitive.

<?php // ==== I don't guarantee this is faster than the PHP 6 before needle, ==== // ==== but it works for PHP below 6 atleast. ==== // ==== IT ALSO HAS INCLUDE NEEDLE BOOLEAN.. ==== function strstrbi($haystack,$needle,$before_needle, $include_needle,$case_sensitive) { $strstr = ($case_sensitive) ? 'strstr' : 'stristr'; if($before_needle!=true && $before_needle!=false && isset($before_needle)){ die('PHP: Error in function '.chr(39).'$strstrbi'. chr(39).' : parameter '. chr(39).'$before_needle'.chr(39).' is not a supplied as a boolean.'); } // END BOOLEAN CHECK '$before_needle' if($include_needle!=true && $include_needle!=false && isset($include_needle)){ die('PHP: Error in function '.chr(39).'$strstrbi'. chr(39).' : parameter '. chr(39).'$include_needle'.chr(39). ' is not a supplied as a boolean.'); } // END BOOLEAN CHECK '$include_needle' if($case_sensitive!=true && $case_sensitive!=false && isset($case_sensitive)){ die('PHP: Error in function '.chr(39).'$strstrbi' .chr(39).' : parameter '. chr(39).'$case_sensitive'.chr(39).' is not a supplied as a boolean.'); } // END BOOLEAN CHECK '$case_sensitive' if(!isset($before_needle)){ $before_needle=false; } if(!isset($include_needle)){ $include_needle=true; } if(!isset($case_sensitive)){ $case_sensitive=false; } switch($before_needle){ case true: switch($include_needle){ case true: $temp=strrev($haystack); $ret=strrev(substr($strstr($temp,$needle),0)); break; // END case true : $include_needle case false: $temp=strrev($haystack); $ret=strrev(substr($strstr($temp,$needle),1)); break; // END case false : $include_needle } break; // END case true : $before_needle case false: switch($include_needle){ case true: $ret=$strstr($haystack,$needle); break; // END case true: $include_needle case false: $ret=substr($strstr($haystack,$needle),1); break; // END case false: $include_needle } break; // END case false : $before_needle } if(!empty($ret)){ return $ret; }else{ return false; } } // === END FUNCTION 'strstrbi' // Example $email = 'user@example.com'; $domain = strstrbi($email, '@', false, false, false); echo $domain; // prints example.com $user = strstrbi($email, '@', true, false, false); echo $user; // prints user ?>

[#9] root at mantoru dot de [2007-11-10 03:22:43]

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 ?>

[#10] gigaman2003 at halfempty dot co dot uk [2007-02-24 12:48:33]

Often you will need to find all occurrences of a string (for security escapes and such)

So I wrote this function to return an array with the locations of all the occurrences. Almost like an advanced strstr.

<?php function findall($needle, $haystack) { //Setting up $buffer=''; //We will use a 'frameshift' buffer for this search $pos=0; //Pointer $end = strlen($haystack); //The end of the string $getchar=''; //The next character in the string $needlelen=strlen($needle); //The length of the needle to find (speeds up searching) $found = array(); //The array we will store results in while($pos<$end)//Scan file { $getchar = substr($haystack,$pos,1); //Grab next character from pointer if($getchar!="\n" || buffer<$needlelen) //If we fetched a line break, or the buffer is still smaller than the needle, ignore and grab next character { $buffer = $buffer . $getchar; //Build frameshift buffer if(strlen($buffer)>$needlelen) //If the buffer is longer than the needle { $buffer = substr($buffer,-$needlelen);//Truncunate backwards to needle length (backwards so that the frame 'moves') } if($buffer==$needle) //If the buffer matches the needle { $found[]=$pos-$needlelen+1; //Add the location of the needle to the array. Adding one fixes the offset. } } $pos++; //Increment the pointer } if(array_key_exists(0,$found)) //Check for an empty array { return $found; //Return the array of located positions } else { return false; //Or if no instances were found return false } } ?>

Haven't had the chance to speed test it, but many optimizations should be possible. It just works enough for me. Hope it saves someone a lot of time.

[#11] leo dot nard at free dot fr [2005-05-24 02:12:18]

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: "??&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; } ?>

[#12] php at silisoftware dot com [2003-02-14 15:37:02]

PHP versions before 4.3.0 (tested on 4.2.2 and 4.2.3) return the $haystack from $needle only up to the first null character. So for example:

<?php $string = strstr("one#two\x00three", "#"); // PHP 4.2.x: $string contains "#two" // PHP 4.3.0: $string contains "#two\x00three" ?>

If you're trying to match nulls, you will probably get back an empty string:

<?php $string = strstr("one#two\x00three", "\x00"); // PHP 4.2.x: $string contains "" // PHP 4.3.0: $string contains "\x00three" ?>