how to get number of days in the month with php

if you want to know number of days in the month with php, you can call function cal_days_in_month()
this function returns the number of days in a given month, based on the calendar, month, and year that you specify

the format of this function is
Cal_days_in_month (calendar, Month, year)
This function have three parameters,

• calendar, you can fill this parameter with CAL_GREGORIAN
  
• month, you can fill this parameter with month (1 - 12)
  
• year, you can fiil this parameter with 4 digits of year (2008)

example :
$days = cal_days_in_month(CAL_GREGORIAN, 1, 2009) ;
echo "In January 2009 there were $days days";
?>

that example will display
In january 2009 there were 31 days