PHP/Language Basics/Php Functions

Functions to Check Data Type

 
Name                  Description
is_null()             Returns true if the value is null (no type)
is_string()           Returns true if the value is a string
is_int()              Returns true if the value is an integer
is_float()            Returns true if the value is a floating-point value
is_array()            Returns true if the value is an array
is_object()           Returns true if the value is an object
is_a()                Deprecated; checks if an object is a specified class
instanceof()          Checks if an object is an instance of a class

Functions to Convert Data Types

 
Function           Description
 
doubleval()        Accepts a value and returns double equivalent
 
intval()           Accepts a value and returns integer equivalent
 
strval()           Accepts a value and returns string equivalent

Functions to Test Data Types

 
Function                   Description
 
is_array()                 Returns true if the argument is an array
 
is_bool()                  Returns true if the argument is boolean
 
is_double()                Returns true if the argument is a double
 
is_int()                   Returns true if the argument is an integer
 
is_object()                Returns true if the argument is an object
 
is_string()                Returns true if the argument is a string
 
is_null()                  Returns true if the argument is null
 
is_resource()              Returns true if the argument is a resource

GMP Functions

 
Name             Description
gmp_abs          Calculates absolute value
gmp_add          Adds numbers
gmp_and          Logical and
gmp_clrbit       Clears bit
gmp_cmp          Compares numbers
gmp_com          Calculates one"s complement
gmp_div_q        Divides numbers
gmp_div_qr       Divides numbers and gets quotient and remainder
gmp_div_r        Remainder of the division of numbers
gmp_div          Alias of gmp_div_q()
gmp_divexact     Exact division of numbers
gmp_fact         Factorial
gmp_gcd          Calculates GCD
gmp_gcdext       Calculates GCD and multipliers
gmp_hamdist      Hamming distance
gmp_init         Creates GMP number
gmp_intval       Converts GMP number to integer
gmp_invert       Inverse by modulo
gmp_jacobi       Jacobi symbol
gmp_legendre     Legendre symbol
gmp_mod          Modulo operation
gmp_mul          Multiplies numbers
gmp_neg          Negates number
gmp_or           Logical or
gmp_perfect_square          Perfect square check
gmp_popcount     Population count
gmp_pow          Raises number into power
gmp_powm         Raises number into power with modulo
gmp_prob_prime   Checks if number is "probably prime"
gmp_random       Random number
gmp_scan0        Scans for 0
gmp_scan1        Scans for 1
gmp_setbit       Sets bit
gmp_sign         Sign of number
gmp_sqrt         Calculates square root
gmp_sqrtrem      Square root with remainder
gmp_strval       Converts GMP number to string
gmp_sub          Subtracts numbers
gmp_xor          Logical xor

Using the @ operator to suppress a warning about the undefined variables

 
<?php 
$scores = array(88, 75, 91, 84); 
list($maths, , $history) = $scores; 
 
@printf("<p>Maths: %d; English: %d; History: %d; Biology: %d.</p>\n", 
$maths, $english, $history, $biology); 
?>