number_format() is one of the most popular PHP function which is used to format numbers with grouped thousands.

Syntax : number_format(number, decimal_values, decimal_point, thousand_separator)

number : The number which has to be formatted.
decimal_values : Specifies number of decimal values after decimal_point.
decimal_point : Specifies the string used as decimal point separator.
thousand_separator : Specifies the string used as thousand separator.

Note :

• The function accepts one, two or four arguments(does not accept three arguments).
• If only first argument is passed, the number is formatted without decimal values and (,) used as thousand separator.
• With two arguments, the number is formatted upto decimal_values passed as argument with (.) as decimal point and (,) as thousand separator.
• With all arguments, the number is formatted upto decimal_values passed as argument, separator for decimal point will be passed as third(decimal_point) argument and fourth(thousand_separator) argument is used as thousand separator.

Examples :

a. Number Formatting with one parameter

<?php
  $number = 1258463.254;
  echo number_format( $number );
?>

Output : 1,258,463

b. Format number with decimal values

<?php
  $number = 1258463.254;
  echo number_format( $number, 2);
?> 

Output :1,258,463.25

c. Format number with all arguments

<?php
  $number = 1258463.254;
  echo number_format( $number, 2, '/', '-');
?> 

Output : 1-258-463/25