Category Archives: PHP

Varnish

Varnish is an HTTP accelerator designed for content-heavy dynamic web sites as well as heavily consumed APIs.

Varnish Cache is a web application accelerator also known as a caching HTTP reverse proxy. You install it in front of any server that speaks HTTP and configure it to cache the contents. Varnish Cache is really, really fast. It typically speeds up delivery with a factor of 300 – 1000x, depending on your architecture.

Varnish stores data in virtual memory and leaves the task of deciding what is stored in memory and what gets paged out to disk to the operating system. This helps avoid the situation where the operating system starts caching data while it is moved to disk by the application.

Furthermore, Varnish is heavily threaded, with each client connection being handled by a separate worker thread. When the configured limit on the number of active worker threads is reached, incoming connections are placed in an overflow queue; when this queue reaches its configured limit incoming connections will be rejected.

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Write a statement to show the joining of multiple comparisons in PHP?

PHP allows multiple comparisons to be grouped together to determine the condition of the statement. It can be done by using the following syntax:
comparison1 and|or|xor comparison2 and|or|xor comparison3 and|or|xor.
The operators that are used with comparisons are as follows:
1. and: result in positive when both comparisons are true.
2. or: result in positive when one of the comparisons or both of the comparisons are true.
3. xor: result in positive when one of the comparisons is true but not both of the comparisons.

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What are the different components used in PHP for formatting?

The components that are used in PHP for formatting are as follows:
1. %: it tells the start of the formatting instruction.
2. Padding character (pad): is used to fill out the string when the value to be formatted is smaller than the width assigned. Pad can be a space, a 0, or any character preceded by a single quote (‘).
3. -: A symbol meaning to left-justify the characters. If this is not included, the characters are right-justified.
4. width: The number of characters to use for the value. If the value doesn’t fill the width, the padding character is used to pad the value. For example, if the width is 5, the padding character is 0, and the value is 1, the output is 00001.
5. dec: The number of decimal places to use for a number. This value is preceded by a decimal point.
6. type: The type of value. Use s(string) for string, f (float) for numbers that you want to format with decimal places.

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How can we increase the execution time of a php script?

By the use of void set_time_limit(int seconds)
Set the number of seconds a script is allowed to run. If this is reached, the script returns a fatal error. The default limit is 30 seconds or, if it exists, the max_execution_time value defined in the php.ini. If seconds is set to zero, no time limit is imposed.
When called, set_time_limit() restarts the timeout counter from zero. In other words, if the timeout is the default 30 seconds, and 25 seconds into script execution a call such as set_time_limit(20) is made, the script will run for a total of 45 seconds before timing out.

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What are the different types of statements that are present in PHP?

There are four kinds of PHP statements that are present. They are as follows:
• Simple statement- these are the echo statements and end with a semicolon (;). PHP ignores white spaces between simple statements. Until it finds a semicolon it reads the statement.
• Complex/Conditional statements: these are the statements which deal with certain conditions that have to be executed to meet certain specific requirements. These are if and else block or switch statements. PHP reads the complete statement and doesn’t stop at the first semicolon it encounters. It looks for starting and ending braces to end the execution.
• Looping statements: statements that are repeated in a block. The feature that enables you to execute the statements repeatedly is called as loop. For example: for loop, while loop, do..while loop.

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