Constants - PHP Questions and Answers

This set of PHP Multiple Choice Questions & Answers (MCQs) focuses on “Constants”.

1. What will be the output of the following PHP code?

```
<?php
```

define("GREETING", "PHP is a scripting language", true);

```
echo GREETING;
```
```
echo "<br>";
```
```
echo GREETING;
```
```
?>
```

a) PHP is a scripting language
b)

GREETING
GREEtING

c) GREETING
d)

PHP is a scripting language
PHP is a scripting language

View Answer

Answer: d
Explanation: Here’, we have defined a constant GREETING. Since the third parameter is true in define(“GREETING”, “PHP is a scripting language”, true), GREETING also becomes case insensitive.

2. What will be the output of the following PHP code?

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```
<?php
```

define("GREETING", "PHP is a scripting language");

```
echo $GREETING;
```
```
?>
```

a) $GREETING
b) no output
c) PHP is a scripting language
d) GREETING
View Answer

Answer: b
Explanation: As you know that Constants do not need a $ before them, they are referenced by their variable names itself. In the given example “GREETING” is a constant. However, if we prefix a $ symbol, we are turning it into a variable, and since there is no variable named GREETING, it won’t echo anything.

3. What will be the output of the following PHP code?

```
<?php
```

define('GREETING_TEST', 'PHP is a scripting language', true);

```
echo GREETING_TESt;
```
```
$changing_variable = 'test';
```

echo constant('GREETING_' . strtoupper($changing_variable));

```
?>
```

PHP is a scripting language PHP is a scripting language

GREETING_TESt PHP is a scripting language

PHP is a scripting language GREETING_TEST

GREETING_TESt GREETING_TEST

View Answer

Answer: a
Explanation: Since the 3rd argument of define() is true, GREETING_TEST becomes case insensitive. So, the “echo GREETING_TESt” will echo “PHP is a scripting language”.

echo constant(x) outputs the value of x, and x here is the concatenation of GREETING_ and $changing_variable converted into uppercase, which results in GREETING_TEST. Next, echo constant(GREETING_TEST) will echo “PHP is a scripting language”.

4. What will be the output of the following PHP code?

```
<?php
```
```
class Constants
```
```
{
```
```
    define('MIN_VALUE', '0.0');  
```
```
    define('MAX_VALUE', '1.0');  
```

    public static function getMinValue()

```
    {
```
```
        return self::MIN_VALUE;
```
```
    }
```

    public static function getMaxValue()

```
    {
```
```
        return self::MAX_VALUE;
```
```
    }
```
```
}
```
```
echo Constants::getMinValue();
```
```
echo Constants::getMaxValue();
```
```
?>
```

a) 0.01.0
b) 01
c) No output
d) ERROR
View Answer

Answer: d
Explanation: In a class constants should be defined const MIN_VALUE = 0.0;const MAX_VALUE = 1.0; instead.

5. What will be the output of the following PHP code?

```
<?php
```

define("__LINE__", "PHP is a scripting language");

```
echo __LINE__;
```
```
?>
```

a) PHP is a scripting language
b) __LINE__
c) 3
d) ERROR
View Answer

Answer: c
Explanation: __LINE__ is a magical constant that gives the current line number and cannot be used as a variable/constant name.

6. What will be the output of the following PHP code?

```
<?php
```
```
define('IF', 42); 
```
```
echo "IF: ", IF;
```
```
?>
```

a) IF:42
b) No output
c) IF:
d) ERROR
View Answer

Answer: d
Explanation: Keyword like IF cannot be used as constant names.

7. What will be the output of the following PHP code?

```
<?php
```

define("NEW_GOOD_NAME_CONSTANT", "I have a value");

define("OLD_BAD_NAME_CONSTANT", NEW_GOOD_NAME_CONSTANT);

```
 
```
```
echo NEW_GOOD_NAME_CONSTANT;
```
```
echo OLD_BAD_NAME_CONSTANT; 
```
```
?>
```

a) I have a value
b) I have a valueI have a value
c) ERROR
d) I have a valueNEW_GOO_NAME_CONSTANTS
View Answer

Answer: b
Explanation: Constants can be set as values for other constants.

8. What will be the output of the following PHP code?

```
<?php
```
```
define('GOOD_OCTAL', 0700);
```
```
define('BAD_OCTAL', 0600);
```
```
print GOOD_OCTAL;
```
```
print '<br>';
```
```
print BAD_OCTAL; 
```
```
?>
```

448
384

0700
0800

c) ERROR
d) No output
View Answer

Answer: a
Explanation: Anything starting from 0 is evaluated as an octal.

9. What will be the output of the following PHP code?

```
<?php
```
```
define("VAR_NAME","test"); 
```
```
${VAR_NAME} = "value"; 
```
```
echo VAR_NAME;
```
```
echo ${VAR_NAME}; 
```
```
?>
```

a) test
b) testtest
c) testvalue
d) error, constant value cannot be changed
View Answer

Answer: c
Explanation: ${VAR_NAME} creates a new variable which is not same as VAR_NAME.

10. What will be the output of the following PHP code?

```
<?php
```
```
class myObject { }
```
```
define('myObject::CONSTANT', 'test');
```
```
echo myObject::CONSTANT; 
```
```
?>
```

a) test
b) error
c) myObject::CONSTANT
d) no output
View Answer

Answer: b
Explanation: Class constants cannot be defined outside class.

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