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.

• explode(' ','php programming makes me explode in my pants.') = Array([0]=>php [1]=>programming [2]=>makes [3]=>me [4]=>explode [5]=>in [6]=>my [7]=>pants.)
• explode(' ','php programming makes me explode in my pants.', 3) = Array([0]=>php [1]=>programming [2]=>makes me explode in my pants.)
• explode(' ','php programming makes me explode in my pants.', -3) = Array([0]=>php [1]=>programming [2]=>makes [3]=>me [4]=>explode)

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.

• nl2br('I love to\nprogram with php.\nIts fun!') =
  I love to
  program with php.
  It's fun!

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]).

• str_pad("php is fun", 20) = php is fun
• str_pad("php is fun", 20, "#") = php is fun##########
• str_pad("php is fun", 20, ":", STR_PAD_BOTH) = :::::php is fun:::::

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

• strlen('I love to program with php!') = 27

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

• If [find] not found returns false.

• strpos('how are you feeling today?', 'you') = 8

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

• If [find] not found returns false.

• stripos('how are you feeling today?', 'you') = 8
• stripos('HOW ARE YOU FEELING TODAY?', 'you') = 8

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.

• str_replace("php", "javascript", "I love php code more than php for breakfast.") = I love javascript more than javascript for breakfast.
• str_replace("php", "javascript", "I love PHP CODE more than php for breakfast.") = I love PHP CODE more than javascript for breakfast.
• str_replace("php", "javascript", "I love php code more than php for breakfast.", $count) = I love javascript code more than javascript for breakfast. $count = 2
• str_replace(explode("|", "lets|php|nap"), explode("|", "can we|javascript|break"), "lets do some php coding and then take a nap.") = can we do some javascript coding and then take a break.

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

• If [find] not found returns false.

• strripos('how are you feeling today you php coder?', 'you') = 26
• strripos('HOW ARE YOU FEELING TODAY YOU PHP CODER?', 'you') = 26

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.

• strstr('how are you feeling today?', 'you') = you feeling today?
• strstr('how are you feeling today?', 'you', true) = how are

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;

• stristr('how are you feeling today?', 'you') = you feeling today?
• stristr('HOW ARE YOU FEELING TODAY?', 'you') = YOU FEELING TODAY?
• stristr('how are you feeling today?', 'you', true) = how are
• stristr('HOW ARE YOU FEELING TODAY?', 'you', true) = HOW ARE

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

• strrev("Is my php programming backwards?") = ?sdrawkcab gnimmargorp php ym sI

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.

• str_split("php is fun") = Array([0]=>p [1]=>h [2]=>p [3]=> [4]=>i [5]=>s [6]=> [7]=>f [8]=>u [9]=>n)
• str_split("php programming is really fun", 5) = Array([0 =>php p [1]=>rogra [2]=>mming [3]=>is r [4]=>eally [5]=>fun)
• str_split("php programming is really fun", 30) = Array([0] =>php programming is really fun)

Converts [$string] to all lowercase letters.

• strtolower('Do you LOVE PHP coding?', 'you') = do you love php coding?

Converts [$string] to all UPPER CASE letters.

• strtoupper('do you love php?') = DO YOU LOVE PHP

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.

• ucfirst('do you love php?') = Do you love php?
• ucfirst('do you LOVE php?', 'you') = Do you LOVE php?
• ucfirst(strtolower('do you LOVE PHP programming?')) = Do you love php programming?

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].

• ucwords('do you love web based programming?') = Do You Love Web Based Programming?

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

• lcfirst('Do you LOVE PHP programming?') = do you LOVE PHP programming?

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].

• substr('how much do you love php?', 9) = do you love php?
• substr('how much do you love php?', -9, 8) = love php

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().

• substr_count("I am a PHP programmer and I love php programming", "php") = 1
• substr_count("I am a PHP programmer and I love php programming", "php", -15) = 1
• substr_count(strtolower("I am a PHP programmer and I love Php programming"),strtolower("php")) = 2; (ignoring case)

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

• substr_replace("How long have you been doing php code?", "I love php code", 0) =
  I love php code
• substr_replace("How long have you been doing php code?", "I love php code", 23) =
  How long have you been I love php code
• substr_replace("How long have you been doing php code?", "I love php code", 23, 22) =
  How long have you been I love php code

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

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

• file_exists($_SERVER['DOCUMENT_ROOT'] . "images/sample-img.png") // returns false if file/path doesn't exist or true if it does.

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.

Possible values for permissions are as follows: permissions number can be combined. For example to set read/write permission 2 + 4 = 6. To set execute/read/write 1 + 2 + 4 = 7.

• 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"])

• move_uploaded_file($file["tmp_name"], $pathToWhereToSave . strtolower(basename($file["name"])));