PHP 8 reference · 61 entries

PHP String Functions

PHP string functions from strlen() and str_replace() to sprintf() and htmlspecialchars(), with syntax, PHP 8 changes and examples you can run.

These functions work on bytes. That's fine for ASCII text, but in UTF-8 a letter like é takes two bytes, so lengths and positions can be off. For user-facing text use the multibyte functions such as mb_strlen() and mb_substr(). Strings are values in PHP: every function returns a new string and leaves the original unchanged.

Name	Description	Since
`strlen()`	Return the length of a string in bytes. Multibyte characters such as é count as several bytes; use mb_strlen() to count characters.	4.0
`str_word_count()`	Count the words in a string, or return them as an array. Words are runs of letters plus ' and -; digits split words.	4.3
`strtolower()`	Convert every ASCII letter in a string to lowercase. Since PHP 8.2 it ignores the locale; use mb_strtolower() for é, Ü and others.	4.0
`strtoupper()`	Convert every ASCII letter in a string to uppercase. Letters such as é stay unchanged; use mb_strtoupper() for those.	4.0
`ucfirst()`	Make the first character of a string uppercase and leave the rest as it is. Only ASCII letters change.	4.0
`lcfirst()`	Make the first character of a string lowercase, leaving the rest unchanged. Handy for turning PascalCase into camelCase.	5.3
`ucwords()`	Uppercase the first letter of each word in a string. By default words are separated by spaces, tabs and new lines.	4.0
`trim()`	Remove whitespace (or other characters you choose) from both ends of a string. Spaces inside the string are kept.	4.0
`ltrim()`	Remove whitespace or other chosen characters from the start (left side) of a string only.	4.0
`rtrim()`	Remove whitespace or other chosen characters from the end (right side) of a string. chop() is an alias.	4.0
`str_pad()`	Pad a string to a given length with spaces or another string, on the right, left or both sides.	4.0
`str_repeat()`	Repeat a string a given number of times and return the result. A count of 0 returns an empty string.	4.0
`strrev()`	Reverse a string byte by byte. Fine for ASCII, but it breaks multibyte characters such as é.	4.0
`str_replace()`	Replace every occurrence of a search string with a replacement. Accepts arrays to make several replacements at once.	4.0
`str_ireplace()`	Replace every occurrence of a search string, ignoring upper and lower case. Otherwise works like str_replace().	5.0
`substr_replace()`	Replace part of a string, given a start position and length, with another string. Also inserts text or masks digits.	4.0
`strtr()`	Translate characters, or replace substrings in one pass using an array of from => to pairs. Longest keys match first.	4.0
`substr()`	Return part of a string, given a start position and an optional length. Negative values count from the end.	4.0
`strpos()`	Find the position of the first occurrence of a substring. Returns false if it's not found, so compare with === false.	4.0
`stripos()`	Find the position of the first occurrence of a substring, ignoring case. Returns false when there's no match.	5.0
`strrpos()`	Find the position of the last occurrence of a substring in a string. Returns false if it isn't found.	4.0
`strstr()`	Return the part of a string from the first occurrence of a substring to the end, or the part before it.	4.0
`strrchr()`	Return the part of a string from the last occurrence of a character to the end. Only the first character of the needle is used.	4.0
`str_contains()`	Check whether a string contains a substring and return true or false. Case-sensitive; added in PHP 8.0.	8.0
`str_starts_with()`	Check whether a string begins with a given substring. Case-sensitive and returns true or false; added in PHP 8.0.	8.0
`str_ends_with()`	Check whether a string ends with a given substring, such as a file extension. Case-sensitive; added in PHP 8.0.	8.0
`substr_count()`	Count how many times a substring occurs in a string. Matches don't overlap, and the search is case-sensitive.	4.0
`explode()`	Split a string into an array by a separator, like turning "a,b,c" into ["a", "b", "c"]. A limit caps the pieces.	4.0
`implode()`	Join array elements into one string with a separator between them. join() is an alias of implode().	4.0
`str_split()`	Split a string into an array of chunks of a given length, one byte each by default. Use mb_str_split() for UTF-8.	5.0
`str_getcsv()`	Parse one line of CSV text into an array of fields, handling quoted values that contain commas or quotes.	5.3
`wordwrap()`	Wrap a string at a given line width by inserting line breaks between words, optionally cutting long words.	4.0
`nl2br()`	Insert an HTML <br> tag before every new line in a string, so plain text keeps its line breaks on a web page.	4.0
`htmlspecialchars()`	Convert &, <, >, " and ' to HTML entities so user text is shown as text, not run as HTML. The main defence against XSS.	4.0
`html_entity_decode()`	Convert HTML entities such as &, < and é back into the characters they stand for.	4.3
`strip_tags()`	Remove HTML and PHP tags from a string, keeping the text. You can allow some tags, but it's no XSS protection.	4.0
`addslashes()`	Add a backslash before quotes, backslashes and NUL bytes. Not a safe way to build SQL: use prepared statements.	4.0
`sprintf()`	Return a formatted string built from a template with placeholders like %s, %d and %.2f. Format numbers, pad and align.	4.0
`printf()`	Output a formatted string, using the same placeholders as sprintf(), and return the number of bytes printed.	4.0
`vsprintf()`	Format a string like sprintf(), but take the values from an array. Useful when the number of values varies.	4.1
`number_format()`	Format a number with grouped thousands and a fixed number of decimals, such as 1,234,567.89 or 1.234,57.	4.0
`strcmp()`	Compare two strings byte by byte, case-sensitively. Returns 0 when equal, less than 0 or more than 0 otherwise.	4.0
`strcasecmp()`	Compare two strings without caring about ASCII upper and lower case. Returns 0 if they match.	4.0
`strncmp()`	Compare only the first n bytes of two strings, case-sensitively. Handy for checking a prefix in older code.	4.0
`strnatcmp()`	Compare strings in natural order, so "img2" comes before "img10" the way people expect. Case-sensitive.	4.0
`strnatcasecmp()`	Compare strings in natural order ("a2" before "a10") while ignoring upper and lower case.	4.0
`similar_text()`	Calculate how similar two strings are, as a count of matching characters and optionally as a percentage.	4.0
`levenshtein()`	Calculate the edit distance between two strings: the fewest insertions, deletions and replacements to turn one into the other.	4.0
`soundex()`	Return a four-character code for how an English word sounds, so names like Robert and Rupert can be matched.	4.0
`md5()`	Calculate the MD5 hash of a string as 32 hex characters. Fine for checksums and cache keys, never for passwords.	4.0
`sha1()`	Calculate the SHA-1 hash of a string as 40 hex characters. Weak for security; prefer hash("sha256", ...).	4.3
`hash()`	Hash a string with the algorithm you choose, such as sha256, sha512, crc32b or xxh3. Returns a hex string.	5.1
`base64_encode()`	Encode binary data or text as Base64, using only letters, digits, + and /, so it travels safely as text.	4.0
`base64_decode()`	Decode a Base64 string back to the original data. With strict mode on, invalid input returns false.	4.0
`urlencode()`	Encode a string for a URL query value: spaces become + and special characters become %XX codes.	4.0
`rawurlencode()`	Encode a string per RFC 3986: spaces become %20. Use it for URL path segments.	4.0
`http_build_query()`	Build a URL-encoded query string, such as page=2&sort=name, from an array. Nested arrays become key[]=... pairs.	5.0
`parse_str()`	Parse a query string such as a=1&b=2 into an array, the reverse of http_build_query(). The result argument is required.	4.0
`ord()`	Return the value (0 to 255) of the first byte of a string, such as 65 for "A". The reverse of chr().	4.0
`chr()`	Return the one-byte character for a value from 0 to 255, such as "A" for 65. The reverse of ord().	4.0
`bin2hex()`	Convert binary data to a hexadecimal string, two hex digits per byte. Often used to print random bytes as a token.	4.0