What is the difference between $ and $$ in php

Make a search before asking net time. However, the criteria for a down vote should be "does not show research effort; is unclear or not useful". I down voted because the question shows no research effort. Add a comment. Active Oldest Votes. Andreas Linden Andreas Linden Lal Quentin Quentin k gold badges silver badges bronze badges.

DhruvThakkar — There are seven explanations here, and a further six beyond the duplicate link, already. If you don't understand any of them then I don't see how I can explain it in a way that you do understand. PHP's loose comparisons can be a huge convenience when used properly! You won't need empty or isset. I'm running PHP 5. This is a correction to one of the previous posts. The loose comparison chart is missing a few things.

So still be wary of string-comparison where both strings might be interpreted as numbers. There is also 0. In php 5. This stems from the use of the UNIX function strtod to convert strings to numbers before comparing.

A quick way to do mysql bit comparison in php is to use the special character it stores. Do note, using the ternary operator shorthand since 5. Before 5. Note: according to the spec, PHP's comparison operators are not transitive. But that may not be what was intended It's a great pitfall even for seasoned programmers and should be looked upon with a great attention. In the table "Comparison with Various Types", please move the last line about "Object" to be above the line about "Array", since Object is considered to be greater than Array tested on 5.

You could check IP to see that I forgot to type my name. Third part is good. Note: The ternary shortcut currently seems to be of no use in dealing with unexisting keys in an array, as PHP will throw an error.

Take the following example. The operator does not work here to suppress this error. Note that typecasting will NOT prevent the default behavior for converting two numeric strings to numbers when comparing them. Note that the "ternary operator" is better described as the "conditional operator". The former name merely notes that it has three arguments without saying anything about what it does.

Needless to say, if PHP picked up any more ternary operators, this will be a problem. If you need nested ifs on I var its important to group the if so it works. The use of 5. Cloud Computing. Data Science. Angular 7. Machine Learning. Data Structures. Operating System. Computer Network. Compiler Design. Computer Organization.