PHP Search & Replace functions

Reference to the search-and-replace functions of PHP, including Regular Expressions.

String Search/Replace functions
Function Returns Does what
ltrim(string [, charlist]) String Removes whitespace from left side of "string"
rtrim(string [, charlist]) String Removes whitespace from right side of "string"
trim(string [, charlist]) String Removes whitespace from both sides of "string"
chr(ascii) String Returns character for Ascii code
ord(string) Integer Returns Ascii code for first character of "string"
str_pad(string, new_length [, pad_string [, pad_type]]) String Pads "string" to "new_length" using "pad_string"
str_repeat(string, multiplier) String Repeats "string" "multiplier" times
str_replace(pattern, new_pattern, string [, count]) String Replaces "pattern" with "new_pattern" in "string"
str_ireplace(pattern, new_pattern, string [, count]) String Replaces "pattern" with "new_pattern" in "string". Case insensitive
strstr(string, pattern [, before_pattern]) String Returns first ocurrence of "pattern" in "string"
stristr(string, pattern [, before_pattern]) String Returns first ocurrence of "pattern" in "string". Case insensitive.
strcspn(string, pattern [, start [, length]]) Integer Returns no. of chars at start of "string" without match in "pattern"
strspn(string, pattern [, start [, length]]) Integer Returns no. of chars at start of "string" matching "pattern"
strpos(string, pattern [, offset]) Integer Returns position of first "pattern" in "string"
stripos(string, pattern [, offset]) Integer Returns position of first "pattern" in "string". Case insensitive.
strrpos(string, pattern [, offset]) Integer Returns position of last "pattern" in "string"
strripos(string, pattern [, offset]) Integer Returns position of last "pattern" in "string". Case insensitive.
strrchr(string, pattern) String Returns end of "string" from last "pattern" to end
strrev(string) String Returns "string" in reverse order
strtok(string, separator) String Breaks "string" into segments, separated by "separator"
strtr(string, pattern, replacement) String Replaces "pattern" with "replacement" in "string"
substr(string, start [, length]) String Returns "length" characters from "start" of "string"
substr_count(string, pattern [, offset [, length]]) Integer Counts no. of times "pattern" is in "string"
substr_replace(string, replacement, start [, length]) Mixed Replaces text in "string" with "replacement", from "start"
str_shuffle(string) String Shuffles characters in "string"
String Compare functions
Function Returns Does what
substr_compare(string1, string2 [, offset [, length [, no_case]]]) Integer Binary safe comparison of two strings. From "offset", up to "length" characters. Default case sensitive
strcasecmp(string1, string2) Integer Binary safe string comparison. Case insensitive.
strcmp(string1, string2) Integer Binary safe string comparison. Case sensitive.
strcoll(string1, string2) Integer Locale based string comparison. Not binary safe, case sensitive.
levenshtein(string1, string2) Integer Returns Levenshtein Distance between two texts
similar_text(string1, string2 [, percent]) Integer Returns a string similarity measure
strncasecmp(string1, string2, length) Integer Binary safe string comparison of the first "length" characters. Case-insensitive
strncmp(string1, string2, length) Integer Binary safe string comparison of the first "length" characters.
strnatcasecmp(string1, string2) Integer Compares using "natural order" algorithm. Case-insensitive
strnatcmp(string1, string2) Integer Compares using "natural order" algorithm.
String Information functions
Function Returns Does what
crc32(string) Integer Returns cyclic redundancy checksum of "string"
md5(string [, raw_out]) String Returns MD5 hash of "string"
hash(algorithm, string [, raw_out]) String Returns hash of "string" using "algorithm" ("md5", "sha256", ...)
metaphone(string [, phonemes]) String Returns Metaphone Key of "string" (similar sound = same key)
soundex(string) String Returns Soundex Key of "string" (similar sound = same key)
strlen(string) Integer Returns length of "string"
str_word_count(string [, format [, charlist]]) Mixed Returns no. of words in "string"
count_chars(string [, mode]) Mixed Returns no. of characters in "string"
POSIX-extended ("regular") RegExp functions
Function Returns Does what
Ereg(regexp, string [, result]) Integer Searches "string" for "regexp", stores result in "result"
ereg_replace(regexp, new_regexp, string) String Replaces "regexp" with "new_regexp", in "string"
Eregi(regexp, string [, result]) Integer Searches "string" for "regexp", stores result in "result". Case insensitive.
eregi_replace(regexp, new_regexp, string) String Replaces "regexp" with "new_regexp", in "string". Case insensitive.
Split(regexp, string [, limit]) Array Splits "string", according to "regexp"
Spliti(regexp, string [, limit]) Array Splits "string", according to "regexp". Case insensitive.
sql_regcase(string) RegExp Retuns a (case-insensitive) RegExp matching "string"
Perl compatible RegExp functions
Function Returns Does what
preg_filter(regexp, new_regexp, string [, limit [, count]]) Mixed Replaces "regexp" with "new_regexp", in "string"
preg_grep(regexp, string [, flags]) Array Returns items in "string" matching "regexp"
preg_last_error() Integer Shows last regexp error
preg_match(regexp, string [, result [, flags [, offset]]]) Integer Searches "string" for "regexp", stores result in "result"
preg_match_all(regexp, string, result [, order [, flags [, offset]]]) Integer Searches "string" for "regexp", stores result in "result", ordered by "order". Global search.
preg_quote(string [, delimiter]) String Escapes regexp chars in "string", adds "delimiter"
preg_replace(regexp, new_regexp, string [, limit [, count]]) Mixed Replaces "regexp" with "new_regexp", in "string"
preg_replace_callback(regexp, callback, string [, limit [, count]]) Mixed Finds "regexp" in "string", does "callback"
preg_split(regexp, string [, limit [, flags]]) Array Splits "string", according to "regexp"

More: