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PHP String strtr() function

The strtr() is an in-built function of PHP, which is used to replace a substring inside the other string. It provides the facility to change the particular word in a string. The strtr() function translates characters or replaces the substrings. It is a case-sensitive function. PHP 4+ versions support this function.

Note: strtr() function replaces a character from all the positions wherever that character is present.

There are some other functions in PHP which are similar to the strtolower() function:


There are two syntaxes available for this function, one for string or character replacement and another one is for array key replacement. These syntaxes are given below.

For string replacement:

There are three arguments in this function. It returns the copy of $str after replacing each character of $from with $to.

For array key replacement:

Here, the above function is containing two arguments. The second argument is $replace_pair, which is in the form of an array('from' => 'to', ?). It will return a string after replacing all the occurrence of array key with the corresponding values.


$str: It is a string parameter which is being translated, means it is the main string which is going to be translated.

$from: It is the next parameter of this function which will be replaced in the string with $to. It is a required parameter unless the array is used.

$to: It is a parameter which will be replaced with $from variable. This parameter is also required as $from unless the array is used.

Note: If from and to have different lengths, then the extra characters of the longer string will be ignored. The length of the returned string $str will be the same.

$replace_pair: This parameter is in the form of an array instead of from and to. This array contains the two strings ($string1 and $string2), i.e., a string1 which needs be changed and string2 to which it is changed.

Note: If string1 and string2 both have different length, then the longer string will be formatted to the length of the shorter string.

Return Value

  • It returns the translated string after replacing $from characters with $to characters.
  • If the passed parameter is array ($replace_pair), then it returns the translated string by changing the key string with the corresponding value. If that array parameter contains a key with an empty string (? ?), then it will return FALSE.


There are a few numbers of examples given below. With the help of these examples, we can understand the working of the strtr() function.

Example 1


Hie! Good Morning


y is replaced with e

u is replaced with o

h is replaced with r

e is replaced with i

So, Hiy! Guud Mohneng is replaced with Hie! Good Morning.

Example 2

PHP program to demonstrate strtr() function when $from and $to have different length.


Hie! Gord Mohning


y is replaced with e

e is replaced with o

u is replaced with r

h is not replaced with any character.

Now, Hiy! Geud Mohneng is replaced with Hie! Gord Mohning.

Example 3

Replacement with array keys


Welcome to javaTpoint.

Example 4

PHP program to demonstrate strtr() function when array key have empty "" string.


No output

Example 5

Multiple replacements with single letter


Welcome to javaTpoemt.


i is replaced with e at multiple places.

n is replaced with m at multiple places.

C is replaced with T only once because this function is case-sensitive.

So, Wilcone to javaCpoint is replaced with Welcome to javaTpoemt rather than Welcome to JavaTpoint.

Example 6



In this example, for the first case, all occurrence of q is replaced with o. On the other hand, Q is not replaced with o because as it is a case-sensitive function.

Good health Good Life.
Gqqd health Gqqd Life.     //case-sensitive

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