I have the following code for PHP
if ($checkimghash != $imghash)
{
the $checkimghash is var_dumped as this array(2) { [0]=> string(40) "da77c24758c6259274bfa171a32d5c4a4a2cb71c" ["PdfHash"]=> string(40) "da77c24758c6259274bfa171a32d5c4a4a2cb71c", the variable $imghash var_dumps as this
string(40) "da77c24758c6259274bfa171a32d5c4a4a2cb71c,
Why is this check running despite the equal results? I thought != needs to pass both type and value checks
Because you are comparing an array to a string and they are not the same
try changing your test to
if ($checkimghash[0] != $imghash)
!= is value, !== is value and type
!= is only comparing the value. It's opposite is ==
TRUE if $a is not equal to $b after type juggling.
!== is comparing both the value and the type. It's opposite is ===
TRUE if $a is not equal to $b, or they are not of the same type.
Source: http://www.php.net/manual/en/language.operators.comparison.php
Edit
The var_dump result in your question is unclear. If you are comparing an array with a string, then they are always different. You may want to compare the value of an element of an array with another string by $array[0]
Because if $checkimghash is an array and $imghash a string then the two won't directly compare (in any meaningful sense), as you're comparing an array (i.e. a collection of strings) to a string! select the element of the array you'd like to compare and use that in the condition.
Related
This question already has answers here:
PHP in_array() / array_search() odd behaviour
(2 answers)
Closed 6 years ago.
$arrValue = array('first', 'second');
$ret = in_array(0, $arrValue);
var_dump($ret);
var_dump($arrValue);
Above example gives following result:
bool(true)
array(2) {
[0]=> string(5) "first"
[1]=> string(6) "second"
}
Why in_array() matches needle 0 to any given haystack?
That's because the function uses a non-strict comparison. The string in the array is compared to integer 0. Some typecasting is happening with data loss, and both are regarded the same:
var_dump(0 == 'first'); // bool(true)
So solve this, you can use the third parameter and set it to true to request strict comparison.
$ret = in_array(0, $arrValue, true);
Keep in mind, through, that strict is really strict. In a strict comparison, 0 is not equal to "0".
Docs: http://nl3.php.net/in_array
Basically here 0 treats as false, so the search will occur like the function in_array search false between your array value. Make it(0) string to get different output.
As php a support strict or non-strict comparison so you need to pass a third value true it tell the to be strict because by default it is non-strict.
For some reason when I iterate through an array using foreach loop a condition fails comparing the key with a string. My array has two indexes the first one is an integer and the second one is an string.
$firmas[] = $credito['acreditado'];
$firmas['cbi'] = "LIC. MARCELA SOTO ALARCÓN";
I want to do something else when the loop finds that the key in that moment is the string one but for some reason when I evaluate the integer index the result is true.
foreach($firmas as $key => $firma){
var_dump($key);
var_dump($key=='cbi');die();
}
The output is
int(0) bool(true)
But as you can see the condition is looking for the string 'cbi' so the result should be false with the integer index and true for the string.
What's happening here?
In PHP, all strings are equal to 0, though not equivalent to it. Try using === instead of just ==.
Addendum: all strings that do not begin with numbers are equal to 0.
I've been reading the PHP Docs on Type Juggling and Booleans but I still don't understand why this comparison evaluates as true. My [incorrect] understanding tells me that in the below if statement, the integer 0 is considered FALSE and "a", being a non-empty string is considered TRUE. Therefore, I expected this comparison to resolve to FALSE == TRUE and ultimately, FALSE. Which part did I get wrong?
<?php
if(0 == "a"){
$result = "TRUE";
}else{
$result = "FALSE";
}
//$result == "TRUE"
?>
http://codepad.viper-7.com/EjxBF5
When PHP does a string <=> integer comparison, it attempts to convert the string to a number in an intelligent way. The assumption is that if you have a string "42" then you want to compare the value 42 to the other integer. When the string doesn't start with numbers, then its value is zero.
From the docs:
The value is given by the initial portion of the string. If the string starts with valid numeric data, this will be the value used. Otherwise, the value will be 0 (zero).
This behavior is also inferred in the comparison docs (look at the first line in the first example).
Your mistake is that you assume operator == coerces each of its operands to boolean before comparing them. It does no such thing.
What happens is that since you are comparing an integer to a string, the string is converted to an integer (in this case "a" converts to 0) and then the comparison 0 == 0 is performed.
It will work if you use a strict comparison === instead of ==. The strict comparison also checks the type of the variables, so 0 === 'a' would be false.
Here is some code I have: (p just echos plus adds a newline)
foreach ($vanSteps as $k => $reqInfo)
{
p($k);
if ('van' == $k) { p('The key is the van, continue'); continue; }//continue if we reached the part of the array where van is key
//do stuff
}
and I'm getting this output:
0
The key is the van, continue
1
2
3
van
The key is the van, continue
Why does the if statement return true when the key is 0? This foreach loop handles logic that applies when the key == 0 (and any other key except if the key is 'van') and this messes up the logic because it's return true when key is 0.
Any help?
Thank you.
Use === for this comparison. When PHP compares string and integer it first casts string to integer value and then does comparison.
See Comparison Operators in manual.
In PHP 'van' == 0 is true. This is because when using == to compare a string and a number, the string is converted to a number (as described in the second link below); this makes the comparison internally become 0 == 0 which is of course true.
The suggested alternative for your needs, would be to use a strict equality comparison using ===.
See Comparison Operators and String conversion to numbers
In PHP, when you compare 2 types, it has to convert them to the same type. In your case, you compare string with int.
Internally this gets converted to
if((int)'van'==0)....
and then
if((int)'van'==1)....
(int)'any possible string' will be 0:) So you either have to manually convert the both values to the same type, or use === as a comparison operator, instead of the loose =.
An exception from this rule(as pointed out in the comments) would be if the string start with a number, or can be interpreted as a number in any way(1, 0002, -1 etc). In this case, the string would be interpreted as a number, diregarding the end of the non-numeric end-of-string
Take a look at http://php.net/manual/en/types.comparisons.php for more details.
This works fine:
$array = array(0=>"a",1=>"b","van"=>"booya!");
function p($v){ echo "{$v}<br />"; }
foreach ($array as $k => $reqInfo)
{
p($k);
if ('van' === $k) { p('The key is the van, continue'); continue; }//continue if we reached the part of the array where van is key
//do stuff
}
Output:
0
1
van
The key is the van, continue
Note the ===.
Read the Comparison with Various Types table
When one of the operand is number, the other operand is converted to number too. Since 'van' is non-numeric sting, it's converted to 0. You should use === operator in the case, which also checks the variable type
That's becuase 'van' == 0 (true).
Instead, you should use 'van' === 0 (false).
In short, use === instead of ==.
Its interpreting the 'van' as a boolean value (false) which 0 is equal to.
To check for exact matches in type and value in PHP you must use === instead of ==
I am using a class which returns me the value of a particular row and cell of an excel spreadsheet. To build up an array of one column I am counting the rows and then looping through that number with a for() loop and then using the $array[] = $value to set the incrementing array object's value.
This works great if none of the values in a cell are 0. The class returns me a number 0 so it's nothing to do with the class, I think it's the way I am looping through the rows and then assigning them to the array... I want to carry through the 0 value because I am creating graphs with the data afterwards, here is the code I have.
// Get Rainfall
$rainfall = array();
for($i=1;$i<=$count;$i++)
{
if($data->val($i,2) != 'Rainfall') // Check if not the column title
{
$rainfall[] = $data->val($i,2);
}
}
For your info $data is the excel spreadsheet object and the method $data->val(row,col) is what returns me the value. In this case I am getting data from column 2.
Screenshot of spreadsheet
Did you try an array_push() ?
array_push($rainfall, $data->val($i,2));
I would use a strict comparison with the not identical operator here instead of using the not equals operator:
if($data->val($i,2) !== 'Rainfall')
If $data->val($i,2) is an integer and you use == both sides will be cast to integers which would give you the result that all integers would work as you expect except for zero. Here's a summary of the difference between == and === when comparing the string "RainFall" with zero:
0 == "RainFall" : true
0 != "RainFall" : false
0 === "RainFall" : false
0 !== "RainFall" : true
I think that the array is treating the 0 like false, which could explain it not going into the array. Would something like this work (if you are using integers)?
(int)($data->val($i,2));
or
(float)($data->val($i,2);)
The problem lies in the if statement. You're trying to compare a string with an integer, which according to the PHP documentation will typecast both to integers.
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.
You can read more here http://php.net/manual/en/language.operators.comparison.php.
Update: The if statement won't work in the case of 0 because (int)"Rainfall" will by typecasted into 0 by PHP causing the statement to be if (0 != 0) { ... }.
If $i represents the row number, why don't you start from 2 instead of 1?