print_vs_echo.php

<?php
$v1 = TRUE;
$v2 = 123;
$v3 = "qqq{$v2}zzz";

// After converting each of its expression's values to strings,
// 'echo' concatenates them in order given, and writes the resulting string to STDOUT.
// 'echo' it does not produce a result.

// After converting its expression's value to a string,
// 'print' writes the resulting string to STDOUT.
// 'print' can be used in any context allowing an expression.
// 'print' it always returns the value 1.

// concatenation
echo   '>>' . $v1 . '|' . $v2 . "<<\n";  // outputs ">>1|123<<"
print  '>>' . $v1 . '|' . $v2 . "<<\n";  // outputs ">>1|123<<"

// multiple expression's
echo   '>>' , $v1 , '|' , $v2 , "<<\n";  // outputs ">>1|123<<"
print  '>>' , $v1 , '|' , $v2 , "<<\n";  // Parse error: syntax error, unexpected ','

// precedence
echo  ('>>' . $v1 . '|' . $v2 . "<<\n"); // outputs ">>1|123<<"
print ('>>' . $v1 . '|' . $v2 . "<<\n"); // outputs ">>1|123<<"

// context in variable
$x = echo "$v3\n";                       // Parse error: syntax error
$x = print "$v3\n";                      // outputs "qqq123zzz"
var_dump($x);                            // outputs "int(1)"

// context in expression statement
$a = $b = 0;
$a > $b ? echo "..." : echo "...";       // Parse error: syntax error
$a > $b ? print "..." : print "...";     // outputs "..."