comparing type string numeric

Question

in php.net the following is written:

If you compare a number with a string or the comparison involves numerical strings, then each string is converted to a number and the comparison performed numerically. These rules also apply to the switch statement. The type conversion does not take place when the comparison is === or !== as this involves comparing the type as well as the value

var_dump("10" == "1e1"); // 10 == 10 -> true
var_dump(100 == "1e2"); // 100 == 100 -> true

why in the first example it is evaluated as true but, the statement $num = (int)"1e1" ; is evaluated as 1 and not 10??? furthermore, why in the second example it is evaluated as true but the statement $num = (int)"1e2" ; is evaluated as 1 and not 100??

stackoverflow.com/questions/11489549/…

Krzysztek
– Krzysztek

2014-01-24 09:35:22 +00:00
Commented Jan 24, 2014 at 9:35 — Krzysztek
– Krzysztek, Commented Jan 24, 2014 at 9:35

Anonymous · Accepted Answer · 2014-01-23 23:18:50Z

1

I am not sure why (int)'1E1' displays 1 (it probably ignores all letters and anything after), but what works perfectly for me is this:

echo '1E1'*1; //returns 10

edited Jan 23, 2014 at 23:18

answered Jan 23, 2014 at 21:07

Anonymous

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2 Comments

user3021621 Over a year ago

if you will run the script you will see that the output is like what I'm saying, and I've tried 1E1 and still turns to 1. my question is why when comparing numerical strings then the it 1E1 is converted to 10 and when I try to convert it by casting to int it is converted to 1????

Anonymous Over a year ago

I updated the answer and I believe I understand what you are asking now.

Krzysztek · Accepted Answer · 2014-01-24 17:59:12Z

0

String and string comparison: "10" is the same string representation as "1e1".
Int and string comparison: 100 as string is "100" or "1e2" and is the same representation as "1e2";
Casting string to int: (int) "1e1" => 1 as intval("1e1").

Casting is not the same as equality.

edited Jan 24, 2014 at 17:59

answered Jan 24, 2014 at 14:30

Krzysztek

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Comments

fejese · Accepted Answer · 2014-04-15 22:44:29Z

0

1e1 is double.

var_dump("10" == "1e1");
// 10 (converts to real type, not int) == 10 (converts to real type, not int) -> true

My attempt to convert the numeric string (float type) to integer:

(int)'1E1'

It turns 1 instead of 100.

edited Apr 15, 2014 at 22:44

fejese

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answered Apr 15, 2014 at 22:19

Boolean_Type

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2 Comments

fejese Over a year ago

This is not really an answer to the question why it is happening

Boolean_Type Over a year ago

To understand why, you need to look at the source code. Otherwise - just accept as fact: it is a feature of parsing strings during conversion to integer (e - is a literal character, it is discarded).

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