10 Useful PHP String-Related Functions

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1. Replace Last Occurrence of a String

1. /**
   
2. * Replace the last occurrence of a string.
   
3. *
   
4. * @param string $search
   
5. * @param string $replace
   
6. * @param string $subject
   
7. * @return string
   
8. */
   
9. function strReplaceLast ( $search, $replace, $subject ) {
   
10. 
    
11.     $lenOfSearch = strlen( $search );
    
12.     $posOfSearch = strrpos( $subject, $search );
    
13. 
    
14.     return substr_replace( $subject, $replace, $posOfSearch, $lenOfSearch );
    
15. 
    
16. }
    

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2. Strip All Non-Alpha Numeric Characters and Spaces

1. /**
   
2. * Remove all characters except letters, numbers, and spaces.
   
3. *
   
4. * @param string $string
   
5. * @return string
   
6. */
   
7. function stripNonAlphaNumericSpaces( $string ) {
   
8.     return preg_replace( "/[^a-z0-9 ]/i", "", $string );
   
9. }
   

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3. Strip All Non-Alpha Numeric Characters

1. /**
   
2. * Remove all characters except letters and numbers.
   
3. *
   
4. * @param string $string
   
5. * @return string
   
6. */
   
7. function stripNonAlphaNumeric( $string ) {
   
8.     return preg_replace( "/[^a-z0-9]/i", "", $string );
   
9. }
   

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4. Remove All Non-Numeric Characters

1. /**
   
2. * Remove all characters except numbers.
   
3. *
   
4. * @param string $string
   
5. * @return string
   
6. */
   
7. function stripNonNumeric( $string ) {
   
8.     return preg_replace( "/[^0-9]/", "", $string );
   
9. }
   

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5. Remove All Non-Alpha Characters

1. /**
   
2. * Remove all characters except letters.
   
3. *
   
4. * @param string $string
   
5. * @return string
   
6. */
   
7. function stripNonAlpha( $string ) {
   
8.     return preg_replace( "/[^a-z]/i", "", $string );
   
9. }
   

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6. Remove All Excess White-Space

1. /**
   
2. * Transform two or more spaces into just one space.
   
3. *
   
4. * @param string $string
   
5. * @return string
   
6. */
   
7. function stripExcessWhitespace( $string ) {
   
8.     return preg_replace( '/  +/', ' ', $string );
   
9. }
   

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7. Format a String for a URL Slug

1. /**
   
2. * Format a string so it can be used for a URL slug
   
3. *
   
4. * @param string $string
   
5. * @return string
   
6. */
   
7. function formatForUrl( $string ) {
   
8. 
   
9.     $string = stripNonAlphaNumericSpaces( trim( strtolower( $string ) ) );
   
10.     return str_replace( " ", "-", stripExcessWhitespace( $string ) );
    
11. 
    
12. }
    

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8. Format an URL Slug into a Human Readable String

1. /**
   
2. * Format a slug into human readable string
   
3. *
   
4. * @param string $string
   
5. * @return string
   
6. */
   
7. function formatFromUrl( $string ) {
   
8.     return str_replace( "-", " ", trim( strtolower( $string ) ) );
   
9. }
   

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9. Get Unique Characters from a String

1. /**
   
2. * Get an array of unique characters used in a string. This should also work with multibyte characters.
   
3. *
   
4. * @param string $string
   
5. * @return mixed
   
6. */
   
7. function getUniqueChars( $string, $returnAsArray=true ) {
   
8.     $unique = array_unique( preg_split( '/(?<!^)(?!$)/u', $string ) );
   
9.     if ( empty( $returnAsArray ) ) {
   
10.         $unique = implode( "", $unique );
    
11.     }
    
12.     return $unique;
    
13. }
    

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10. Generate a Random String

1. /**
   
2. * Generate a random string of specified length from a set of specified characters
   
3. *
   
4. * @param integer $size Default size is 30 characters.
   
5. * @param string $chars The characters to use for randomization.
   
6. */
   
7. function randomString( $size=30, $chars="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789" ) {
   
8. 
   
9.     $string = "";
   
10.     $length = strlen( $chars );
    
11. 
    
12.     for( $i=0; $i < $size; $i++ ) {
    
13.         $string .= $chars{ rand( 0, $length ) };
    
14.     }
    
15. 
    
16.     return $string;
    
17. 
    
18. }
    

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