Educator

Introduction to Functions

• A function is a group of PHP statements that can be executed on request by other PHP code using what’s known as a function call .
• When reaching a function call, PHP halts execution of the current script, executes the function’s section of code, and then returns to executing the original script.
• A function call is made by typing name of the function followed by a pair of parentheses.
• Function arguments are expressions that can be 'passed' to a function by placing them in a comma-separated list between the parentheses of a function call.
• Functions are themselves expressions and thus have a value. The value of a function is called its return value , and this value is 'returned' to the calling script.
• Functions can be chained together by using the return value of one function as an argument to another.
• php.net provides documentation, via a function reference , for all of the built-in functions PHP makes available to programmers. The documentation provides function prototypes , which are descriptions of the arguments a particular function accepts along with what type of data value it returns.
• Functions in PHP can be defined to take optional arguments . In the php.net function reference, optional arguments are denoted in a function’s prototype by placing them within pairs of square brackets.
• Additonal Resources:
  • PHP Manual Function Reference
  • Function Reference - String Functions
  • Function Reference - Array Functions
  • Function Reference - Date & Time Functions
  • PHP Manual - Timezone Identifiers