CODEWITHSUNDEEP
phpstringreplacepreg-replace
Dylan
Dylan

Reputation: 9373

Remove a part of a string, but only when it is at the end of the string

I need to remove a substring of a string, but only when it is at the END of the string.

for example, removing 'string' at the end of the following strings :

"this is a test string" ->  "this is a test "
"this string is a test string" - > "this string is a test "
"this string is a test" -> "this string is a test"

Any idea's ? Probably some kind of preg_replace, but how??

Upvotes: 94

Views: 74338

Answers (10)

mickmackusa
mickmackusa

Reputation: 47894

There are multiple techniques which can be used to remove a needle string from the end of another string. All snippets below will perform correctly even on multibyte strings. Some functions have nuanced behaviors which will be described.

Using preg_replace() will seamlessly allow replacements on an array of haystack strings which may spare the need to manually implement a loop. preg_replace() can offer more tooling around case-insensitivity, whole-word matching, and potentially cleaning up unwanted spaces or punctuation before the match (if desired). When passing a dynamic string value to a preg_ function, it is recommended to escape characters in the string with special meaning to the regex engine.

Codes: (PHPize Demo)

  1. Use quoting markers around the needle in the pattern. This saves a preg_quote() call, but could be broken if the needle contains \E.

    function rtrimNeedle1(string|array $haystack, string $needle): string|array {
    return preg_replace("/\\Q$needle\\E$/u", '', $haystack);
}

  2. Using preg_quote() will be the most reliable way to escape characters in the needle string. This is probably the method that I would use professionally because it doesn't need to faff around with conditions. Because the pattern delimiter is #, preg_quote() doesn't need a second parameter -- this is not true if the pattern delimiters are forward slashes.

    function rtrimNeedle2(string|array $haystack, string $needle): string|array {
    return preg_replace('#' . preg_quote($needle) . '$#u', '', $haystack);
}

  3. Conditionally use substr_replace() to remove the unwanted suffix.

    function rtrimNeedle3(string $haystack, string $needle): string {
    return !str_ends_with($haystack, $needle)
        ? $haystack
        : substr_replace($haystack, '', -strlen($needle));
}

  4. Conditionally use substr() to isolate the leading characters before the needle.

    function rtrimNeedle4(string $haystack, string $needle): string {
    return !str_ends_with($haystack, $needle)
        ? $haystack
        : substr($haystack, 0, -strlen($needle));
}

  5. Conditionally use mb_substr() and mb_strlen() to isolate the leading characters before the needle.

    function rtrimNeedle5(string $haystack, string $needle): string {
    return !str_ends_with($haystack, $needle)
        ? $haystack
        : mb_substr($haystack, 0, -mb_strlen($needle));
}

Notice that the non-mb_ functions behave identically to the mb_ function because the offset and length parameters of substr_replace() and substr() both operate on bytes, not characters. Because mb_substr()'s parameters are characters, mb_strlen() must be used in the length parameter.

Upvotes: 0

avpaderno
avpaderno

Reputation: 29679

With PHP 8, the code can be simpler.

function right_trim(string $haystack, string $needle): string {
  if (str_ends_with($haystack, $needle)) {
    return substr($haystack, 0, -strlen($needle));
  }

  return $haystack;
}

Upvotes: 0

Artem
Artem

Reputation: 1646

PHP 8 version

function removePostfix(string $haystack, string $needle): string
{
    if (str_ends_with($haystack, $needle)) {
        return substr($haystack, 0, strlen($haystack) - strlen($needle));
    }


    return $haystack;
}

Upvotes: 1

Skrol29
Skrol29

Reputation: 5552

Using regexp may fails if the substring has special characters.

The following will work with any strings and follows conventions used by built-in string functions:

function right_trim(string $haystack, string $needle): string {
    $needle_length = strlen($needle);
    if (substr($haystack, -$needle_length) === $needle) {
        return substr($haystack, 0, -$needle_length);
    }
    return $haystack;
}

Upvotes: 37

tklodd
tklodd

Reputation: 1079

@Skrol29's answer is the best, but here it is in function form and using the ternary operator:

if (!function_exists('str_ends_with')) {
    function str_ends_with($haystack, $suffix) {
        $length = strlen( $suffix );
        if( !$length ) {
            return true;
        }
        return substr( $haystack, -$length ) === $suffix;
    }
}

if (!function_exists('remove_suffix')) {
    function remove_suffix ($string, $suffix) {
        return str_ends_with($string, $suffix) ? substr($string, 0, strlen($string) - strlen($suffix)) : $string;
    }
}

Upvotes: 0

Marco Panichi
Marco Panichi

Reputation: 1185

IF you don't mind about performance AND the part of the string could be placed only at the end of string, THEN you can do this:

$string = "this is a test string";
$part = "string";
$string = implode( $part, array_slice( explode( $part, $string ), 0, -1 ) );
echo $string;
// OUTPUT: "this is a test "

Upvotes: 0

Bas
Bas

Reputation: 3096

I wrote these two function for left and right trim of a string:

/**
 * @param string    $str           Original string
 * @param string    $needle        String to trim from the end of $str
 * @param bool|true $caseSensitive Perform case sensitive matching, defaults to true
 * @return string Trimmed string
 */
function rightTrim($str, $needle, $caseSensitive = true)
{
    $strPosFunction = $caseSensitive ? "strpos" : "stripos";
    if ($strPosFunction($str, $needle, strlen($str) - strlen($needle)) !== false) {
        $str = substr($str, 0, -strlen($needle));
    }
    return $str;
}

/**
 * @param string    $str           Original string
 * @param string    $needle        String to trim from the beginning of $str
 * @param bool|true $caseSensitive Perform case sensitive matching, defaults to true
 * @return string Trimmed string
 */
function leftTrim($str, $needle, $caseSensitive = true)
{
    $strPosFunction = $caseSensitive ? "strpos" : "stripos";
    if ($strPosFunction($str, $needle) === 0) {
        $str = substr($str, strlen($needle));
    }
    return $str;
}

Upvotes: 13

Errico Malatesta
Errico Malatesta

Reputation: 179

preg_replace and this pattern : /string\z/i

\z means end of the string

http://tr.php.net/preg_replace

Upvotes: 2

Pascal MARTIN
Pascal MARTIN

Reputation: 400972

I suppose you could use a regular expression, which would match string and, then, end of string, coupled with the preg_replace() function.


Something like this should work just fine : 
$str = "this is a test string";
$new_str = preg_replace('/string$/', '', $str);

Notes :
  • string matches... well... string
  • and $ means end of string

For more informations, you can read the Pattern Syntax section of the PHP manual.

Upvotes: 7

user142162
user142162

Reputation:

You'll note the use of the $ character, which denotes the end of a string:

$new_str = preg_replace('/string$/', '', $str);

If the string is a user supplied variable, it is a good idea to run it through preg_quote first:

$remove = $_GET['remove']; // or whatever the case may be
$new_str = preg_replace('/'. preg_quote($remove, '/') . '$/', '', $str);

Upvotes: 142

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