PHP Functions Cheat Sheet

Break apart [$string] into an array of parts, splitting [$string] at each occurrence of [$separator].

• [$number_of_array_parts] is a number that restricts the number of array parts produced via explode(). If [$number_of_array_parts] is a positive number, if for example your use of explode() would normally produce 10 array items and you specify 5 for [$number_of_array_parts], explode will stop breaking apart the string at the [$number_of_array_parts] and the last array element will contain the remaining string.
• If [$number_of_array_parts] is a negative number then explode() will chop off ending array elements which will be minus what you specify for [$number_of_array_parts]. For example your use of explode() would normally produce 10 array items and you specify -5 for [$number_of_array_parts], explode will return the first 5 array elements, chopping of the last 5 elements.
• see the companion function join() which is the opposite of explode() which takes an array and joins it together as a single string.

Takes the parts of an [$array] and joins them into a string.

• [$join_character] is the character to insert between each of the array parts to create the finished string. [$join_character] is optional and if omitted, an empty string "" is the default.
• If [$join_character] is omitted, the correct syntax for implode is implode($array).
• see the companion function explode() which is the opposite of implode() which takes a string and breaks it apart into an array.

Function to insert proper HTML break tags to ensure a new line is output everwhere \n occurs in [$string]. The optional boolean [$xhtml_compatible] specified whether html line breaks are the more standard <br> or the XHTML compatible version of that which is <br/>.

• The function parameter [$xhtml_compatible], in most cases does not need to be supplied and can be ignored.

Check to see if $string has or contains $strLookingFor.

• Similar to php strpos() function.
• str_contains() IS case sensitive. To do a case insensitive search use php function stripos().

Make a string a specific length so even if the actual string is shorter than [$output_length] [$string] gets padded so the final length is [$output_length]. Generally used for visual formatting purposes.

• [$padding_string] is the character(s) to be used for the padding. The default is whitespace.
• [$padding_type] where the padding is placed:
  • [1]STR_PAD_RIGHT (default - padding right side of [$string])
  • [2]STR_PAD_LEFT (padding left side of [$string])
  • [3]STR_PAD_BOTH (padding both sides of [$string]).

Find all instances of [$find] in [$string] and replace each of them with [$replacement]. [$return_number_replacements] is an optional variable that returns to you the number of replacements found.

• Use strtolower() on $string and $find to make str_replace case ignored.
• To perform multiple replacements use explode() on $find and $replacement.

Split [$string] into an array, each element of the array being the length of [$each_arr_len].

• If [each_arr_len] is ommited, the default length of 1 for each array element is the default.
• If [each_arr_len] is larger than the length of [string] then the entire [string] will be returned as the only array element.

Returns the length number of characters of [$string].

Returns position of first occurrence of [$find] within [$string].

• If [find] not found returns false.

Returns position of first occurrence of [$find] within [$string].

• If [find] not found returns false.

Returns position of last occurrence of [$find] within [$string].

• If [find] not found returns false.

Finds first occurrence of [$find] within [$string] and returns everything from the start of [$find] to the end.

• If [return_before] set to true, the part of the string before [find] is returned.
• If [find] not found returns false.

Finds first occurrence of [$find] within [$string] and returns everything from the start of [$find] to the end.

• If [return_before] set to true, the part of the string before [find] is returned.
• If [find] not found returns false;

Takes [$string] and reverses the characters so the string read backwards.

Converts [$string] to all lowercase letters.

Converts [$string] to all UPPER CASE letters.

Converts first character of [$string] to upper case and leaves the rest of [$string] alone. To make an entire [$string] lower case with first letter capitalized use strtolower() to lowercase the entire [$string] first.

Converts first letter of each word of [$string] to upper case. To capitialize just the first letter of the first word of [$string] use function [ucfirst].

Converts first character of [$string] to lower case and leaves the rest of [$string] alone.

Returns part of [$string] starting at [$startpos] and is the length of [$length].

• If [length] is omitted, the entire string from [startpos] is returned.
• A [startpos] of a negative number starts at that many characters backwards from the end of [string].

Returns how many times [$substring] can be found within [$string] with [$start] being the start position to start searching for [$substring] within [$string] and [$length] being the endpoint of the search.

• If [start] is a negative number then the substring search starts at that many character position backwards from the end of the string.
• To make this function ignore case, make [string] and [substring] lower case first with strtolower().

Replace [$string] or part of [$string] with [$replacement]. If [$start] = 0 and [$length] argument omitted, entire [$string] replaced with [$replacement].

Create an array on the fly.

• [$startIndex] is most typically 0 as this is the default of arrays in php but the $startIndex can be and number.

Create an array by modifying the elements of an existing array $arrToMap1 via function $functionToMap.

• $functionToMap can be an external function that is used but unless the $functionToMap is long or complicated, using an anonymous function directly within array_map $functionToMap is more concise and a better way to go.
• Built in PHP function can be used for $functionToMap. Just surround the PHP function name within quotes ie "strtoupper".

Combine/merge 2 or more arrays as a single new array.

• If any array elements have the same key, the last one overrides the others.

Search an array $arrayToSearch for a value $whatToSearchFor. Returns the key of $arrayToSearch of the matching $whatToSearchFor, if found or returns false.

• array_search is case sensitive so a value of "Hello" in $whatToSearchFor will not find "hello" in the array. See example below how to deal with this.
• Optional $strictMatch if true, only returns a match if a value identical in type and value to $whatToSearchFor, is found in $arrayToSearch. For example if you search for the string "10" it will not return a match for integer 10.
• array_search works on both indexed and associative arrays however with associative array they key of the found match is return instead of its index number.
• To search a multidimensional array more than one level you would need to use a recursive search function.

To perform a case insensitive search using array_search ...

Remove and return the first element of $array.

Removes any duplicates in array to ensure each element of $array is unique.

• $sortType is optional and can be:
       SORT_STRING (default): compares items in $arr as strings
       SORT_REGULAR: compare items normally, doesn't change types
       SORT_NUMERIC: compares item numerically
       SORT_LOCALE_STRING: compare items as strings, based on current locale.

Insert new element(s) to the beginning of an array.

• New elements $itemToAdd1, [$itemToAdd2, $itemToAdd3, ...] get inserted at the beginning of the array in the order supplied.

See if $searchFor can be found as an element in $arr. Returns TRUE if found or FALSE.

• in_array() only seaches a flat or single level array and not a multidimensional array. To do this you would need to flatten the multidimensional array or perform a recursive search.
• [$type] (true/false) if true, performs a strict search meaning if [$type] = false in_array() will return TRUE for both 1 and "1" if $arr contains either 1 or "1". If [$type] = true then the value as well as the type being searched for must match exactly.

Returns [true/false] whether file or path [$path_to_check] exists.

• Results are cached. Use clearstatcach() to clear the cache.

Creates a directory you specify via [$path]. Returns [true/false]. For [$path] you should use server path ie /var/www/html/project/newdirectory and not internet path https://website.com/project/newdirectory

[$permissions] is a 4 digit number which refers to read/write permissions of the newly created directory.

• 1st # is always 0.
• 2nd # indicates permissions for the owner.
• 3rd # indicates permissions for the owners user group.
• 4th # is permissions for anyone else.

• 1 = execute permisions.
• 2 = write permissions.
• 4 = read permissions.

• example #1: 0644 = read/write permissions for owner and read only for everyone else.
• example #2: 0777 = read/write/execute permissions for all not recommended

If [$recursive] set to false, only the last directory item after the last / is created. If [$recursive] set to true, any parts of [$path] are created that don't exist.

Takes a file uploaded via POST ie $file["tmp_name"] and places in the location specified by [$to].

• The name of the file can be changed from the original $file["name"] by specifying the new name being part of the [$to] string, just be sure the appropriate file extension exits at the end of [$to].
• For security its a good idea to not just move the uploaded file using $file["name"] but instead basename($file["name"])

Saves php errors so they can be analyzed/debugged. These error messages can be sent to a log, file, or email address. The return is either true on success

$err_message = the text of the error message you want reported/printed.

[$err_dest_type] = where the error message will be saved or printed or output.

• 0 = (default) file location of the error_log configuration set in the php.ini file.
• 1 = sent to email address specified in [$err_sent_to].
• 3 = save to a file location specified by [$err_sent_to].

[$err_sent_to] = where the error message will saved/sent/printed.

• if [$err_dest_type] = 0 this parameter is not needed/used.
• if [$err_dest_type] = 1 sent to email this would be an email address.
• if [$err_dest_type] = 3 saved to file location this would be the local server file path ie $_SERVER["DOCUMENT_ROOT"] . "/files/err.log". use full, absolute and not relative paths ie "/files/err.log".

[$email_headers] is only used if [$err_dest_type] = 1 sent to email. Specifies email headers, like From, Cc, and Bcc. Multiple headers should be separated with a line break \r\n