Asked  8 Months ago    Answers:  5   Viewed   36 times

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php == vs === operator
How do the equality (== double equals) and identity (=== triple equals) comparison operators differ?

Why does the following statement return true?

"608E-4234" == "272E-3063"

I have also tried this with single quotes around the strings. The only way I can get it to evaulate to false is by using the === operator instead of ==

My guess is PHP is treating it as some sort of equation but it seems a bit of a strange one.

Can anybody elaborate?

 Answers

66

"608E-4234" is the float number format, so they will cast into number when they compares.

608E-4234 and 272E-3063 will both be float(0) because they are too small.

For == in php,

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.

http://php.net/manual/en/language.operators.comparison.php

Attention:

What about the behavior in javascript which also has both == and ===?

The answer is the behavior is different from PHP. In javascript, if you compare two value with same type, == is just same as ===, so type cast won't happen for compare with two same type values.

In javascript:

608E-4234 == 272E-3063 // true
608E-4234 == "272E-3063" // true
"608E-4234" == 272E-3063 // true
"608E-4234" == "272E-3063" // false (Note: this is different form PHP)

So in javascript, when you know the type of the result, you could use == instead of === to save one character.

For example, typeof operator always returns a string, so you could just use

typeof foo == 'string' instead of typeof foo === 'string' with no harm.

Wednesday, March 31, 2021
 
Puneet
answered 8 Months ago
46

A regex would be simplest:

$input = 'foo_left.jpg';
if(!preg_match('/_(left|right|center)/', $input, $matches)) {
    // no match
}

$pos = $matches[0]; // "_left", "_right" or "_center"

See it in action.

Update:

For a more defensive-minded approach (if there might be multiple instances of "_left" and friends in the filename), you can consider adding to the regex.

This will match only if the l/r/c is followed by a dot:

preg_match('/(_(left|right|center))./', $input, $matches);

This will match only if the l/r/c is followed by the last dot in the filename (which practically means that the base name ends with the l/r/c specification):

preg_match('/(_(left|right|center))\.[^\.]*$/', $input, $matches);

And so on.

If using these regexes, you will find the result in $matches[1] instead of $matches[0].

Wednesday, March 31, 2021
 
braindamage
answered 8 Months ago
66

First of all, is it possible that you just want to use a diverging colormap, 'neutral' at zero, and diverging to two distinct colours? This is an example:

import matplotlib.pyplot as plt
import numpy as np

v1 = -1+2*np.random.rand(50,150)
fig,ax = plt.subplots()
p = ax.imshow(v1,interpolation='nearest',cmap=plt.cm.RdBu)
cb = plt.colorbar(p,shrink=0.5)
ax.set_xlabel('Day')
ax.set_ylabel('Depth')
cb.set_label('RWU')
plt.show()

enter image description here

If you really want to use two different colormaps, this is a solution with masked arrays:

import matplotlib.pyplot as plt
import numpy as np
from numpy.ma import masked_array

v1 = -1+2*np.random.rand(50,150)
v1a = masked_array(v1,v1<0)
v1b = masked_array(v1,v1>=0)
fig,ax = plt.subplots()
pa = ax.imshow(v1a,interpolation='nearest',cmap=cm.Reds)
cba = plt.colorbar(pa,shrink=0.25)
pb = ax.imshow(v1b,interpolation='nearest',cmap=cm.winter)
cbb = plt.colorbar(pb,shrink=0.25)
plt.xlabel('Day')
plt.ylabel('Depth')
cba.set_label('positive')
cbb.set_label('negative')
plt.show()

enter image description here

Thursday, July 29, 2021
 
jeremyharris
answered 3 Months ago
61

This can't work properly. Stored with Unicode there are many more Characters than with ANSI. So if you "convert" to ANSI, you will loose lots of charackters.

http://php.net/manual/en/function.htmlentities.php

You can use Unicode (UTF-8) charset with htmlentities:

string htmlentities ( string $string [, int $flags = ENT_COMPAT [, string $charset [, bool $double_encode = true ]]] )

htmlentities($myString, ENT_COMPAT, "UTF-8"); should work.

Thursday, August 5, 2021
 
CoderGuy123
answered 3 Months ago
38

You can use array_map:

$arrKeys = array('str', 'str', 'otherStr');
$arrVals = array('1.22', '1.99', '5.17');
function foo($key, $val) {
   return array($key=>$val);
}

$arrResult = array_map('foo', $arrKeys, $arrVals);

print_r($arrResult);
Array
(
    [0] => Array
        (
            [str] => 1.22
        )

    [1] => Array
        (
            [str] => 1.99
        )

    [2] => Array
        (
            [otherStr] => 5.17
        )

)

BTW, if you upgrade to PHP 5.3 you can do this using an anonymous function, which is a bit more elegant:

array_map(function($key, $val) {return array($key=>$val);}, $arrKeys, $arrVals);
Wednesday, August 11, 2021
 
Chase
answered 3 Months ago
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