PHP: IF condition

Question

Is there any difference between following two IF conditions?

if ($insert_id)
{
..
}



if($insert_id != NULL)
{
..
}

Actually a function returns the mysql insert id, and i want to check if the function returned id or not.

mysql function return boolean FALSE on error, and other thigns on success. They should never be returning null. — Marc B
– Marc B, Commented Jul 8, 2011 at 21:14
@Marc B, so if theres some mysql error and it doesnt return the insert_id, will the first condition true even then? Which method i should use to make sure that condition is true only if an integer (insert_id) is returned. In all other cases it should be false. — Roman
– Roman, Commented Jul 8, 2011 at 21:19
No, it'd still be false, because the failure turned a false. you can explicitly test with if ($result_from_mysql === FALSE) { ... failure ... }. — Marc B
– Marc B, Commented Jul 8, 2011 at 22:12

Xeoncross · Accepted Answer · 2011-07-08 21:14:03Z

1

NULL is loosely equal to FALSE, Zero, and an empty string.

Study this table to learn about comparisons.

Basically,

$value = NULL;

if($value == FALSE) // True
if($value == '') // True
if($value == 0) // True
while...
if($value === FALSE) // False
if($value === '') // False
if($value === 0) // False

answered Jul 8, 2011 at 21:14

Xeoncross

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Comments

graup · Accepted Answer · 2011-07-08 21:17:12Z

0

No, there's no difference.

There would be if you used !== NULL. If it's just != NULL it will also evaluate against false, '' (empty string) or the integer value 0.

The same goes for the first statement, which is short for $insert_id == true which is basically the same as != false or != NULL.

answered Jul 8, 2011 at 21:17

graup

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Comments

Brian · Accepted Answer · 2011-07-08 21:14:30Z

0

If the $insert_id belongs to a resultset returned by a mysql_query, then use the first one:

if ($insert_id)
{
    // do stuff
}

answered Jul 8, 2011 at 21:14

Brian

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Comments

Dejan Marjanović · Accepted Answer · 2011-07-08 21:17:51Z

0

if (!empty($insert_id))
{

}

if($insert_id > 0)
{

}

answered Jul 8, 2011 at 21:17

Dejan Marjanović

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Comments

The Mask · Accepted Answer · 2011-07-08 21:18:47Z

0

In the php language,you not need return an expression booleana(what is correct). any something different of: 0,false,null and ""(empty string) is parsed as true

answered Jul 8, 2011 at 21:18

The Mask

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Comments

bitbandit · Accepted Answer · 2011-07-08 21:26:40Z

0

For what you're trying to do there is no difference.

Basically what you're trying to do is see if the variable is set. Since any non-zero expression is essentially true, if there is a value it will evaluate as such.

The only time it would matter is if you were specifically checking for a NULL value.

answered Jul 8, 2011 at 21:26

bitbandit

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