関連ワード:  define function in php with example    what is function in php with example    user defined function in php with example    system defined function in php with example    explain user defined function in php with example    what is library function in php with examples    what is function in php explain its type with example    what is function in php please tell syntax with example    explain user defined functions in php with suitable example    how to define and use function in php explain with example