PHP: Extract string from string

I have this kind of a String which I get from an API Get-request:

HTTP/1.1 404 Not Foundset-cookie: test-usercontext=asdf-client=200; path=
/set-cookie: test=AjQxMDMBABhNAEEATgBHAE8AIAAgACAAIAAgACAAIAACAAYyADAAMAADABBGAEIAVAAgACAAIAAgACAABAAYMgAwADEANgAwADQAMgA4ADEAMAAzADQABQAEAAAACAYAAlgACQACRQD
%2fA%2fowggP2BgkqhkiG9w0BBwKgggPnMIID4wIBATELMAkGBSsOAwIaBQAwCwYJKoZIhvcNAQcBoIICwjCCAr4wggJ%21AgcgE
wUWFQk1MAkGByqGSM44BAMwRTELMAkGA1UEBhMCREUxDzANBgNVBAoTBlNBUC1BRzEMMAoGA1UECxMDRkJUMRcwFQYDVQQDDA4qL
ndkZi5zYXAuY29ycDAeFw0xMzA1MTYxNTA5MzVaFw0zODAxMDEwMDAwMDFaMEUxCzAJBgNVBAYTAkRFMQ8wDQYDVQQKEwZTQVAtQUcxDDAKBgNVBAsTA0ZCVDEXMBUGA1UEAwwOKi53ZGYuc2FwLmNvcnAwggG4MIIBLAYHKoZIzjgEATCCAR8CgYEA
%2f%21RvacHcYrHXGs0tkbb0V5pRZr%2166wpEefngcrA%2feo5VUyPFnjV%21VLPgYTlK5oVBT%21b8hVdVDF72%2fF7tG%2fzyNXjr6xCkACw69
%21NEBKQ4A7RSfLieN8IgCWl3ENA6cbgQJlhYMAugQexgN5rNX67eLyIFTEHGbF%2fkvlWXyDZt2AsCFQCCZiO7z37X8dHkeMyzasFRThlyFwKBgQC6
%2f4ZVeZJsMH528dpoLej8jEeUYstPpe6CFgIF7LqFjFnEWM%2fgt364k9%21kYRMdnN1l3Dgv2fHBOMET2lwiCSP%21Lp3JkDH9K
%21H9zLJfg%2fd3o5gNCu4pct9Au4%2fLh%21ejlgOAytMcr7z9G1SSaRKFk9QnzfyA4mmLmtDT6qZG%2fgx5%21wOBhQACgYEA%21rGBozVMIrQFy8mXlkOSDWiAo16gBBlLqAIhsc3Th
%2f6LFM%21HK8mzuxApdB8vDg5zOPQW959g2YmZBvMm7fBjjRyeQnh0SamBQNwdWR3cyhdXANRJTjdjV6yGJaBVUzMam5Yh2%2fNjwHWxS
%21Ev%21KNSUi7%2fHLrYjQ%2f5mYiipmBwOskwCQYHKoZIzjgEAwMvADAsAhQkPKrX2UIzsWHZoErU9zMKRjRMSwIUchu3vWrhXc2bckO
%21ASRCiCh3oF4xgf0wgfoCAQEwUDBFMQswCQYDVQQGEwJERTEPMA0GA1UEChMGU0FQLUFHMQwwCgYDVQQLEwNGQlQxFzAVBgNVB
AMMDioud2RmLnNhcC5jb3JwAgcgEwUWFQk1MAkGBSsOAwIaBQCgXTAYBgkqhkiG9w0BCQMxCwYJKoZIhvcNAQcBMBwGCSqGSIb3D
QEJBTEPFw0xNjA0MjgxMDM0NTdaMCMGCSqGSIb3DQEJBDEWBBTLTQarxV7dyga8cQOmMUBQNBc4mTAJBgcqhkjOOAQDBC4wLAIUUOp
%21DiZu22HaQ324gaZTLbbjWqICFCtwUwws0te2HqBON0OF%2faQ%21hLD3; path=/; domain=test.de; secure; HttpOnlyset-cookie
: asdf_SESSIONID=VMoFGADsOTEThFHqCdDaC9mG0O4NLBHmhakAUFaDZVE%3d; path=/; secure; HttpOnlycontent-type
: application/jsoncontent-length: 504x-csrf-token: dZgtpkwUMaN-gQ1X4QEXUw==dataserviceversion: 1.0x-asdf-e2eperf
: { asName: "ldai1_00", asType: "asdf", elapsed: 319, maxMem: 4595, dbTime: 166 }{"error":{"code"
:"005056A509B11EE1B9A8FEC11C21D78E","message":{"lang":"en","value":"Resource not found for the segment
 'http:'."},"innererror":{"transactionid":"5721AEEC42F83183E10000000A4DA014","timestamp":"20160428103457
.6579540","Error_Resolution":{"error","Note":"Note 1797736
 for error analysis"}}}}<br>

I want to extract the X-CSRF-Token, which is listed after: x-csrf-token:.

In this case it would be

dZgtpkwUMaN-gQ1X4QEXUw==

How do I do this the best way?

Do I use preg_match_all? But what then, I am a bit lost. Thank you for any advice.

Solution

This regex will work

x-csrf-token:(.*?)(?=\w+:)

Regex Demo

PHP Code

$re = "/x-csrf-token:(.*?)(?=\\w+:)/m"; 
preg_match_all($re, $str, $matches);
print_r($matches[1]);

Ideone Demo

A better solution will be to stop when there is space besides \w+: (assuming spaces cannot be part of x-csrf-token)

x-csrf-token:\s*(.*?)(?=\w+:|\s)