check if there are only letters or numbers on string php code example

Example 1: check value contains numbers or letters php

ctype_digit(string text);

Parameter Used:
The ctype_digit() function in PHP accepts only one parameter.

text : Its mandatory parameter which specifies the tested string.

Return Values:
It returns TRUE if all characters of the string are numeric otherwise 
  return FALSE.
  
Input  : '789495001'
Output : TRUE
Explanation : All digits, return True

Input  : 'adc123' or '789.0877'
Output : FALSE
Explanation: String contains number and string or floating point, 
return false.

Example 2: check value contains numbers or letters php

is_numeric ( $var ) 
  returns : true or false

'42' is numeric
1337 is numeric
1337 is numeric
1337 is numeric
1337 is numeric
1337.0 is numeric
'0x539' is NOT numeric
'02471' is numeric
'0b10100111001' is NOT numeric
'1337e0' is numeric
'not numeric' is NOT numeric
array (
) is NOT numeric
9.1 is numeric
NULL is NOT numeric