Php interview Questions - part6

How do you call a constructor for a parent class?

parent::constructor($value)

WHAT ARE THE DIFFERENT TYPES OF ERRORS IN PHP?

Here are three basic types of runtime errors in PHP:

1. Notices: These are trivial, non-critical errors that PHP encounters while executing a script - for example, accessing a variable that has not yet been defined. By default, such errors are not displayed to the user at all - although you can change this default behavior.

2. Warnings: These are more serious errors - for example, attempting to include() a file which does not exist. By default, these errors are displayed to the user, but they do not result in script termination.

3. Fatal errors: These are critical errors - for example, instantiating an object of a non-existent class, or calling a non-existent function. These errors cause the immediate termination of the script, and PHP's default behavior is to display them to the user when they take place.

Internally, these variations are represented by twelve different error types

What’s the special meaning of __sleep and __wakeup?

__sleep returns the array of all the variables than need to be saved, while __wakeup retrieves them.

How can we submit a form without a submit button?

If you don't want to use the Submit button to submit a form, you can use normal hyper links to submit a form. But you need to use some JavaScript code in the URL of the link. For example:

href="javascript: document.myform.submit();">Submit Me

Why doesn’t the following code print the newline properly? php $str = ‘Hello, there.\nHow are you?\nThanks for visiting fyicenter’; print $str; ?>

Because inside the single quotes the \n character is not interpreted as newline, just as a sequence of two characters - \ and n.

Would you initialize your strings with single quotes or double quotes?

Since the data inside the single-quoted string is not parsed for variable substitution, it’s always a better idea speed-wise to initialize a string with single quotes, unless you specifically need variable substitution.

How can we extract string 'abc.com ' from a string http://info@abc.com using regular expression of php?

We can use the preg_match() function with "/.*@(.*)$/" as 

the regular expression pattern. For example: 

preg_match("/.*@(.*)$/","http://info@abc.com",$data);

echo $data[1];

What is the difference between the functions unlink and unset?

unlink() is a function for file system handling. It will simply delete the file in context.

unset() is a function for variable management. It will make a variable undefined.