why result of this Comparing is true - php

Question

in this simple PHP code
why php parser return true?
$text="51.406ABC917";
$floatval = floatval($text);//51.406
if($floatval==$text){
$result_compare = true;//php parser return true
}else{
$result_compare = false;
}

Answer 1

It's about Type Juggling and PHP type comparison tables, and Comparison Operators. Just check it.
Type of Operand 1:string, resource or number
Type of Operand 2: string, resource or number
Translate strings and resources to numbers, usual math.
You could avoid convertion to float by adding typecasting to string.
if((string)$floatval==$text){
$result_compare = true;
}else{
$result_compare = false; //php parser return false
}

Answer 2

== will compare the data ,use === to compare data and datatype

Answer 3

$floatval==$text
in the above comparison you are comparing a float value with a string
try with === instead of ==

Answer 4

Look here . You should never compare floats for equality.
You need use the epsilon technique.
For example:
if (abs($forstFloat - $secondFloat) < epsilon) {
echo 'they are equal!!'
}
where epsilon is constant representing a very small number.

Answer 5

$a == $b Equal TRUE if $a is equal to $b after type juggling.
$a === $b Identical TRUE if $a is equal to $b, and they are of the same type.
Take this as example
<?php
var_dump(0 == "a"); // 0 == 0 -> true
var_dump("1" == "01"); // 1 == 1 -> true
var_dump("10" == "1e1"); // 10 == 10 -> true
var_dump(100 == "1e2"); // 100 == 100 -> true
switch ("a") {
case 0:
echo "0";
break;
case "a": // never reached because "a" is already matched with 0
echo "a";
break;
}
?>
Reference

Answer 6

Try this,
$text="51.406ABC917";
$floatval = floatval($text);//51.406
if($floatval===$text){
$result_compare = 'true';//php parser return true
}else{
$result_compare = 'failed';
}
LOGIC:
$a == $b Equal TRUE if $a is equal to $b after type juggling.
$a === $b Identical TRUE if $a is equal to $b, and they are of the same type.
Ref: http://www.php.net/manual/en/language.operators.comparison.php

Answer 7

Before comparison $text is converted to a float , with same result as floatval(),
then you compare $floatval==$text, so result is pretty predictable - TRUE
It's normal, when you compare variables from 2 different types, first them to be converted to closest same type.
I would suggest, when comparing float, use similar construct
if ( abs($floatval - floatval($text)) < 0.001 ) {..}
compare difference between 2 floats, instead them. Cause if u have 2 numbers, 45 and 45.00001 , php will think they differ.
What do you wanna accomplish ? Why you think this result is wrong ?

Answer 8

try this:
<?php
$text="51.406ABC917";
$floatval = floatval($text);//51.406
if(strval($floatval)==$text){
$result_compare = true;//php parser return true
}else{
$result_compare = false;
}
?>

Answer 9

If first part of string is numbers, it will be converted to numbers otherwise it will be zero (0). Yes, to compare value and type of variable, use === instead of ==.
But in your case, you already convert string to float by floatval($text); then === same as ==.
The problem is how php convert string to number by floatval($text);
This is how php convert string to numbers:
<?php
$foo = 1 + "10.5"; // $foo is float (11.5)
$foo = 1 + "-1.3e3"; // $foo is float (-1299)
$foo = 1 + "bob-1.3e3"; // $foo is integer (1)
$foo = 1 + "bob3"; // $foo is integer (1)
$foo = 1 + "10 Small Pigs"; // $foo is integer (11)
$foo = 4 + "10.2 Little Piggies"; // $foo is float (14.2)
$foo = "10.0 pigs " + 1; // $foo is float (11)
$foo = "10.0 pigs " + 1.0; // $foo is float (11)
?>
Full document here: http://www.php.net/manual/en/language.types.string.php#language.types.string.conversion