php 基础笔记 boolean integer float

/***************************by
garcon1986********************************/
<?php
// boolean integer float example
$action = false;
if($action == "show version"){
echo "the version is 123".'<br>';
}else if($action == false){
echo "action is false".'<br>';
}else {
echo "action is true".'<br>';
}
//some var_dump exercise ---------- var_dump print the relational information of variables
var_dump((bool)""); //bool(false)
var_dump((bool) 1); //bool(true)
var_dump((bool) 0); //bool(false)
var_dump((bool) -1); //bool(true)
var_dump((bool) -2); //bool(true)
var_dump((bool) "foo"); //bool(true)
var_dump((bool) 2.3e5); //bool(true)
var_dump((bool) array()); //bool(false)
var_dump((bool) array(12)); //bool(true)
var_dump((bool) "false"); //bool(true)
//var_dump
$a = 3;
$b = "s1";
//$c = var_dump($a); // int(3)
$d = var_dump($a, $b);
var_dump((bool)00190); // bool(true)
var_dump(00190); // int(1)
$large_number = 2147483647;
var_dump($large_number);
// output: int(2147483647)
$large_number = 2147483648;
var_dump($large_number);
// output: float(2147483648)
// it's true also for hexadecimal specified integers between 2^31 and 2^32-1:
var_dump( 0xffffffff );
// output: float(4294967295)
// this doesn't go for hexadecimal specified integers above 2^32-1:
var_dump( 0x100000000 );
// output: int(2147483647)
$million = 1000000;
$large_number = 50000 * $million;
var_dump($large_number);
// output: float(50000000000)
var_dump(25/7); //output float(3.5714285714286)
var_dump((int)(25/7)); // int(3)
var_dump((boolean)(25/7));// boolean(true)
var_dump(round (25/7)); // float(4)
//special conditions Warning:Never cast an unknown fraction to integer, as this can sometimes lead to unexpected results.
echo (int)((0.1+0.7)*10); // echoes 7!
echo (int)((0.26-0.1)*100); //echoes 16
?>