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PHP Interview Questions

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You can use the string concatenation operator (.) to join two strings into one. Here is a PHP script example of string concatenation:

<?php
echo 'Hello ' . "world! ";
?>

This script will print:

Hello world!

PHP supports 3 string comparison operators, <, ==, and >, that generates Boolean values. Those operators use ASCII values of characters from both strings to determine the comparison results. Here is a PHP script on how to use comparison operators:

<?php
$a = "PHP is a scripting language.";
$b = "PHP is a general-purpose language.";
if ($a > $b) {
print('$a > $b is true.'." ");
} else {
print('$a > $b is false.'." ");
}
if ($a == $b) {
print('$a == $b is true.'." ");
} else {
print('$a == $b is false.'." ");
}
if ($a < $b) {
print('$a < $b is true.'." ");
} else {
print('$a < $b is false.'." ");
}
?>

This script will print:

$a > $b is true.
$a == $b is false.
$a < $b is false.

In a string context, PHP will automatically convert any numeric value to a string. Here is a PHP script examples:

<?php
print(-1.3e3);
print(" ");
print(strlen(-1.3e3));
print(" ");
print("Price = $" . 99.99 . " ");
print(1 . " + " . 2 . " = " . 1+2 . " ");
print(1 . " + " . 2 . " = " . (1+2) . " ");
print(1 . " + " . 2 . " = 3 ");
print(" ");
?>

This script will print:

-1300
5
Price = $99.99
3
1 + 2 = 3
1 + 2 = 3

The print() function requires a string, so numeric value -1.3e3 is automatically converted to a string "-1300". The concatenation operator (.) also requires a string, so numeric value 99.99 is automatically converted to a string "99.99". Expression (1 . " + " . 2 . " = " . 1+2 . " ") is a little bit interesting. The result is "3 " because concatenation operations and addition operation are carried out from left to right. So when the addition operation is reached, we have "1 + 2 = 1"+2, which will cause the string to be converted to a value 1.

In a numeric context, PHP will automatically convert any string to a numeric value. Strings will be converted into two types of numeric values, double floating number and integer, based on the following rules:

  • 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).
  • If the valid numeric data contains '.', 'e', or 'E', it will be converted to a double floating number. Otherwise, it will be converted to an integer.

You can use the "strlen()" function to get the number of characters in a string. Here is a PHP script example of strlen():

<?php
print(strlen('It's Friday!'));
?>

This script will print:

12

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