print function outputs a string
int print (string $arg)
print() is not actually a real function (it is a language construct) so you are not required to use parentheses with its argument list.
Various Method of Using print:
echo — Output one or more strings
void echo ( string $arg1 $arg2 );
Outputs all parameters.
echo() is not actually a function (it is a language construct), so you are not required to use parentheses with it. echo() (unlike some other language constructs) does not behave like a function, so it cannot always be used in the context of a function. Additionally, if you want to pass more than one parameter to echo(), the parameters must not be enclosed within parentheses.
Various Method of Using echo:
sprintf returns a string produced according to the formatting string format. Type Specifier that says what type the argument data should be treated as. The conversion specifiers are useful to format or transform the values. Each conversion specifier starts with a single percent symbol%) and ends with a conversion character (one ofb, c,d,f,o,s, u,x, orX ). Please refer http://in2.php.net/manual/en/function.sprintf.php for complete list of specifiers along with descriptions.
Hello world. Day number 123
Prints human-readable information about a variable
print_r (mixed $expression [, bool $return])
print_r() displays information about a variable in a way that's readable by humans. print_r(), var_dump() and var_export() will also show protected and private properties of objects with PHP 5. Static class members will not be shown. Remember that print_r() will move the array pointer to the end. Use reset() to bring it back to beginning. Main practical use of print_r() function is to output array values.
[a] => apple
[b] => banana
[c] => Array
 => x
 => y
 => z
Var_dump is used to get information about a variable. This function displays structured information about one or more expressions that includes its type and value. Arrays and objects are explored recursively with values indented to show structure. In PHP 5 all public, private and protected properties of objects will be returned in the output.
The echo and print functions are similar is all aspects. The only difference between them is that when items are separated using a comma, the echo function performs faster.