OOP Basics

/**
 * Instances CANNOT use private and protected members
 * Children CAN inherit only public and protected members
 */
class MyClass
{
    public $name = 'John';
    protected $username = 'JohnT23';
    private $password = 'secret';

    function printAll()
    {
        echo "From class MyClass:";
        echo $this->name." ";
        echo $this->username." ";
        echo $this->password." ";
    }
}

$obj = new MyClass();
echo "From Instance \$obj:".$obj->name."\n"; //Works
//echo $obj->username; // Fatal Error
//echo $obj->password; // Fatal Error
$obj->printAll();

echo"\n<br>";

class MyClass2 extends MyClass
{
    // We can re-declare/access the public and protected method
    // but not private ones
    function printAll()
    {
        echo "From class MyClass2:";
        echo $this->name." ";
        echo $this->username." ";
        // Children cannot access private member of parent
        // echo $this->password; // Error
    }
}

$obj2 = new MyClass2();
echo "<br>
 From Instance \$obj2:".$obj2->name; // Works
//echo $obj->username; // Fatal Error
//echo $obj->password; // Fatal Error
$obj2->printAll();

Testing File Permission for file upload and database connectivity

On a freshly installed Linux server you need to test file permission and database connectivity.
Here are some scripts that can help you with that:

Git protocol on server and client side

This is an advanced tutorial for experienced users that are familiar with git, SSH protocols and shell scripts.
 
On server side

[user@test_server ~]$ git daemon --base-path=/var/www/html --reuseaddr  --export-all --verbose --enable=receive-pack 

Do not close the terminal on server.

 --base-path=/var/www/html is path to your repository.

Two Way Encryption

Two way encryption on PHP works with mcrypt extension enabled.
Here's a simple snippet that uses password and generates different encryption string every time you reload.

<?php
$string = "This is a string to be encrypted";
$key = "This is a key";
// Encryption Algorithm
$alg = MCRYPT_TWO_FISH;
// Create the initialization vector for added security
$iv = mcrypt_create_iv(mcrypt_get_iv_size($alg, MCRYPT_MODE_ECB), MCRYPT_RAND);
// Output original string
print "Original string: $string <p>";
// Encrypt $string
$encrypted_string = mcrypt_encrypt($alg, $key, $string, MCRYPT_MODE_CBC, $iv);
// Convert to hexadecimal and output to browser
print "Encrypted string: ".bin2hex($encrypted_string)."<p>";
$decrypted_string = mcrypt_decrypt($alg, $key, $encrypted_string, MCRYPT_MODE_CBC, $iv);

print "Decrypted string: $decrypted_string";
?>

A short video how code works

Two aliases for the same MySQL table

Here's how to establish database relationships between connected entities. In this example we'll use a highways map. The final query will show city names and highway that connects them in  result set rows.

Map of highways:

Connections between cities

Git most used features

Cache credentials if you need to enter credentials only once and they are cached for 900 seconds

git config credential.helper 'cache --timeout=3000'

Create branch from an existing branch and switch to it

git checkout -b new_branch develop

Create branch from commit and switch to it

git checkout -b new_branch d9410d98f69d08

Diff between local and remote branch

git fetch
git difftool origin/develop develop
# to refresh develop branch
git pull

Delete branches that don't exist on remote repo - sync remote and local repo

# git remote prune origin
* [pruned] origin/branch_name
# git branch -d branch_name # manually remove orphan

comparing files in two revisions

# this will launch diff tool for one file in two revisions
$ git difftool 344c f8cc proba.txt

# this will launch diff tool for one file in commit and working directory
$ git difftool  a9a5f2a ./component.ts

# Usage of difftool for comparing all files in two revisions
git difftool 8c6a dd6b

Compare current commit with previous one

git difftool HEAD..HEAD~1

Put in zip archive files from single commit

git archive -o latest.zip HEAD

My favorite format for log

git log --pretty=format:"%C(#cd9a00)%h %C(#0080ff) <%an> %C(#17b062)(%cr) %d %C(#c0d6de)%s"

remove ajax.php from version control but not from file system

git rm --cached ajax.php 
git commit -m 'removed ajax.php from git'

put file from past commit to index and view diff.

git checkout 42cf1ad -- package.json
git difftool --cached

Search every branch in Git Repository and find commit containing messageb or regex search fin.*me in specified time range and print hash, line number and lines around matching line.

# in PowerShell and Linux
git grep -in -C 1 messageb $(git rev-list --all)
git grep -in -C 1  fin.*me $(git rev-list --all --since="2021-05-10" --before="2021-05-26")

another useful when looking for source code in all branches

# search in all files in all branches
# only Linux
git rev-list --all | (
    while read revision; do
        git grep -F 'yourWord' $revision
    done
)

to find branch with SHA

$ git branch -a --contains 08d70aa131ded0ca84f9d31b7
newmain

search all commit messages in all branches

git log --all --oneline | grep "yourWord"

How single file changed in past by time and between commits

git log --follow -p  --since="2 hours ago"  -- README.md
git log --follow -p  HEAD~3..HEAD -- README.md

List commits for my_branch since it's creation

git log --pretty=format:"%C(#cd9a00)%h %C(#0080ff) <%an> %C(#17b062)(%cr) %d %C(#c0d6de)%s" master..my_branch

Solve conflict, merge and refresh feature branch from master

git checkout -b my-branch # create new branch from master
# modify line, commit & push
# in GitLab modify same line add commit on master 
# create merge request, try to merge it - it fails
git checkout master
git pull # refresh local copy
git checkout my-branch
git merge master
# merge, commit & push
# merge my-branch into master in GitLab using merge request

Install diff and merge tool for Windows: 1.Install KDiff3 2.Place this in .gitconfig file

[difftool "kdiff3"]
    path = "c:/Program Files/KDiff3/kdiff3.exe"
    trustExitCode = false
[difftool]
    prompt = false
[diff]
    tool = kdiff3
[mergetool "kdiff3"]
    path = "c:/Program Files/KDiff3/kdiff3.exe"
    trustExitCode = false
[mergetool]
    keepBackup = false
[merge]
    tool = kdiff3

jQuery animate and queue

Simple HTML with two div elements that shows jQuery's animate and queue effects.

Yellow paragraph simultaneously changes height and width.
Grey paragraph first changes height and then width.