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].

Returns the values from a single column in the input $array.

• Input $array is a multidimensional array.
• If [$indexKey] is supplied it will be the column to use as the index/keys for the returned array.

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.

Filter out certain elements of an array.

• [$filteringFunction], if not provided, array_filter() function will remove any falsey values from $array ie false, null, 0, "0", "" (empty string), [] (empty array).
• [$filteringFunction] can either be an external function that filters $array or an inline function.
• [$flag] can either be the constant ARRAY_FILTER_USE_KEY or ARRAY_FILTER_USE_BOTH. If [$flag] is not specified the value of each array element is passed to the callback function [$filteringFunction]. If [$filteringFunction] is not provide then the $value of [$flag] is ignored.
• If the [$flag] of ARRAY_FILTER_USE_KEY is specified then the $array keys are passed to [$filteringFunction] so $array should be an associative array.
• If the [$flag] ARRAY_FILTER_USE_BOTH is specified then BOTH the associative array keys and values are passed to [$filteringFunction].

Find and return as an array the values of any array elements of the first argument of array_intersect() $mainArray exist in ALL remaining arguments ie $arrToCheck1, $arrToCheck2, etc.

• By default, array_intersect() is not a strict comparison type is not checked so if $mainArray contained the array element "3", if any of the succeeding arrays contained either 3 or "3" they both would be returned as a match.
• array_intersect() only compares the values of the arrays while array_intersect_assoc() performs a more strict comparison and looks at both the keys and the values.

Find and return as an associative array the keys and the values of any array elements of the first argument of array_intersect_assoc() $mainArray exist in ALL remaining arguments ie $arrToCheck1, $arrToCheck2, etc. Both the keys and the values have to match to be returned.

• array_intersect_assoc() performs a more strict comparison and looks at both the keys and the values of array elements while array_intersect() only compares the values of the arrays. If you need to make sure both value and type match then use array_intersect_assoc().

Search $array to see if the array key of $key exists.

• While array_key_exists() is more suited for an associative array for obvious reasons, array_key_exists() will still work on a non associative array because a non associative array also has keys, which are numeric indices.

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.
• in_array() search array values while array_key_exists() searches the keys of an associative array.
• [$type] (true/false) if true, performs a strict search meaning if [$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